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Timber FrameIsometric cut-away view
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Detail 3.00
Structural timber frame
Vapour control layer
Insulation
Wall ties
Cavity
Outer leaf (brick shown)
Sheathing board
Breather membrane
Timber batten /service void (option)
Rigid insulation /plasterboard composite
LegendInsulation zone
Air tightness barrier(note: this can alsoact as a vapourcontrol layer)
Guidance on thermalcontinuity
Blue text
Guidance on airtightness
Red text
General guidance notes
Alternative constructions1. The rigid insulation / plasterboard
construction can be replaced otherfinishes but this will require that thickerinsulation is used in the wall. Ensurethat the thermal conductivity of thisinsulation is equal or less than thatused in the cavity of the timber frame,to prevent interstitial condensationproblems.
2. Different constructions can be used toprovide an outer leaf but check thatthere is sufficient ventilation provisionto prevent moisture from being trappedwithin the wall.
Sealing membrane junctions3. All membranes should be taped,
stapled or bedded in adhesive asidentified by manufacturer. Repair alltears in membranes beforecommencing next stage of work.
Psi-value calculations4. For details of all thermal conductivity
values of materials used in thepsi-value calculations, see Appendix Bof the Introduction.
Material λ-values usedin calculations(W/mK)
Plasterboard 0.21Insulation (generic) 0.04Plywood sheathing 0.13Brick outer leaf 0.77Mineral wool insulation 0.044Concrete block(dense) protected
1.13
Concrete block(lightweight, high strength)
0.19
Timber frame 0.13Concrete floor beam 2.3Concrete screed 1.15Render (cement/sand) 1.0Gypsum plaster(1000kg/m3)
0.4
Concrete roof tiles 1.5EPDM membrane 0.25Timber battens 0.13Timber flooring 0.13Chipboard 0.13Floor joists 0.13Aluminium 160Steel 50Stainless steel 17Glass 1Sarking felt 0.23Insulation board 0.022
Values used in psi calculations
Timber FramePitched Roof: Ventilated Roofspace - EavesPsi value = 0.0464W/mK
Thermal continuity checklist
1. Ensure that insulation layers in roof arefitted perpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timberframe insulation
3. Install cavity barrier at the top of the wall.
Detail 3.01
Proprietary cross flowventilator to maintainminimum 25mm air gap
Ventilation gap equivalent to10mm minimum continuousopening is required whereroof pitch is above 15°orventilation gap equivalent to25mm minimum continuousopening is required wherethe roof pitch is below 15°
Vapour control layer inwall and ceiling
Ventilation gap equivalent to 5mmminimum continuous opening at ridgeis required where the roof pitch isgreater than 35° or the roof span ismore than 10m
Insulation between the studsmust be tightly fitted leaving no
gaps
Cavity barrier giving 30 minutefire resistance - ensure cavitybarrier is not breeched byinappropriate rigid sheathinginsulation material
Timber batten to providefixing for plasterboard sheet
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.02 and 3.21 forother junctions using this roof construction
20x38mm timber battens /services void (optional)
Composite rigid insulation /plasterboard
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps and is robustly joinedto the barrier in the ceiling
Timber FramePitched Roof: Ventilated Roofspace - GablePsi value = 0.1006W/mK Detail 3.02
Loft insulation continued upto outer face of the rigidsheathing
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Vapour control layer inwall and ceiling
Cavity ventilator
Timber runner to provide fixingfor plasterboard sheet
Insulation between thestuds must be tightly fitted
leaving no gaps
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.01 and 3.21 forother junctions using this roof construction
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps and is robustly joinedto the barrier in the ceiling
Thermal continuity checklist
1. Ensure that insulation layers in roof arefitted perpendicularly, to cover junctions
2. Ensure that roof insulation butts against the timber sheathing in the wall
3. Install cavity barrier at the top of the wall.
Full depth dwang required tosecure roof bracing at a levelabove the rafter ties.Alternative batten and bracingdetails can also be used
Timber FramePitched Roof: Ventilated Rafter Void - GablePsi value = 0.0472W/mK Detail 3.03
Thermal continuity checklist
1. Ensure that insulation is fitted tightly withinthe timber frame
2. Ensure that insulation layers in roof arefitted perpendicularly to cover junctions
3. Install cavity barrier at the top of the wall.
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in theceiling
Masonry built upbetween ladder legs
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Vapour control layer inwall and ceiling
Cavity ventilator
Timber runner to provide fixingfor plasterboard sheets
Insulation between thestuds must be tightly fitted
leaving no gaps
Minimum 50mm ventilation path over insulation
Where two insulation types areused together see
supplementary guidance
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.04, 3.05 and 3.22for other junctions using this roof construction
Note: this construction istypically used where thereare habitable rooms withinthe roof construction
Timber FramePitched Roof: Ventilated Batten Void (warm roof) - EavesPsi value = 0.0284W/mK Detail 3.04
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in theceiling
Rigid insulation used as sarking.Insulation to be vapour permeable
Proprietary overfascia ventilator
Vapour control layer inwall and ceiling
Cavity barrier giving 30 minutefire resistance - ensure cavity
barrier is not breeched byinappropriate rigid sheathing
insulation materialInsulation between the
studs must be tightlyfitted leaving no gaps
Timber batten to provide fixingfor plasterboard sheets
Ventilation tobatten void
Vapour permeable membrane(with a vapour resistance ofnot more than 0.6MN.s/g)
Lap roof and wall insulationminimum 150mm thickness atnarrowest point
Ventilation gap equivalent to5mm minimum continuousopening is required at ridgeto batten space
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.03, 3.05 and 3.22for other junctions using this roof construction
Thermal continuity checklist
1. Ensure that insulation layers in roof arefitted perpendicularly, to cover junctions
2. Ensure that roof insulation overlaps with the top of the timber frame wall, with minimum 50mm overlap at the narrowest point
3. Install cavity barrier at the top of the wall
Alternative position forplasterboard ceiling
Note: this construction istypically used where thereare habitable rooms withinthe roof construction
Timber FramePitched Roof: Ventilated Batten Void (warm roof) - GablePsi value = 0.0431W/mK Detail 3.05
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in theceiling
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Vapour control layer inwall and ceiling
Cavity ventilator
Insulation between the studs mustbe tightly fitted leaving no gaps
Minimum 50mm ventilation path over insulation
Where two insulation types areused together see
supplementary guidance
Vapourpermeablemembrane(with a vapourresistance ofnot more than0.25 MN.s/g)
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.03, 3.04 and 3.22for other junctions using this roof construction
Compressible filler
Thermal continuity checklist
1. Ensure that insulation layers are fittedperpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timberframe insulation
3. Install cavity barrier at the top of the wall.
Timber runner to provide fixingfor plasterboard sheets
Note: this construction istypically used where thereare habitable rooms withinthe roof construction
Timber FrameTimber Flat RoofPsi value = 0.0536W/mK Detail 3.06
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in theceiling
Verge - tightly fit insulationinto void over wall andunder deck (not shown)
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Vapour control layer in wall
Cavity ventilator Timber batten to be provided tocover over junction between
plasterboard sheets
Insulation between thestuds must be tightly fitted
leaving no gaps
Compressible filler
Eaves - fix full height blockingpiece and tightly fit insulation intovoid and under deck
Vapour control layer turned up edgeof roof insulation, lapped with roofwaterproofing layer and sealed
Membrane roof construction
Vapour control layer in ceiling
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling2. A vapour barrier is required at ceiling
level, to prevent moisture from enteringinto the roof construction
3. The option shown here includes a vapourcontrol layer and insulation as part of amembrane roof construction. Similardetails could be used for a profiled metaldecking roof but consult withmanufacturer regarding ventilationrequirements.
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Thermal continuity checklist
1. Ensure that insulation layers in roof arefitted perpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timberframe insulation
3. Install cavity barrier at the top of the wall.
Timber FrameTimber Flat Roof with ParapetPsi value = 0.0299W/mK Detail 3.07
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in theceiling
Cavity barriergiving 30 minutefire resistance -ensure cavitybarrier is notbreeched byinappropriate rigidsheathinginsulation material
Vapour control layer inwall and ceiling
Insulation between the studs must betightly fitted leaving no gaps
Compressible fillerRoofing membrane to be taken minimum
150mm above finished roof level
Vapour control layer turned up edgeof roof insulation, lapped with
breather membrane from cavity wall
Tightly fit compressible insulant between the wallstuds above the level of the roof deck
Vapour control layer
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling2. A vapour barrier is required at ceiling
level, to prevent moisture from enteringinto the roof construction
3. The option shown here includes a vapourcontrol layer and insulation as part of amembrane roof construction. Similardetails could be used for a profiled metaldecking roof but consult withmanufacturer regarding ventilationrequirements.
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WRoof - 9.500(m²K)/W
Thermal continuity checklist
1. Ensure that insulation layers in roof arefitted perpendicularly, to cover junctions
2. Ensure that roof insulation butts against the timber wall sheathing with a minimum of 50mm overlap at narrowest point
3. Install cavity barrier at the top of the wall
Timber FrameLintel at Window HeadPsi value = 0.121W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier around opening
Air tightness checklist
1. Install window to overlap with outer leaf ofwall finish.
Alternative:If window lines through with the bottom ofthe opening in the external finish, somemeans of preventing a direct line of airinfiltration will be required
2. Install air tightness seal between theinside face of the window and thestructural finish of the window opening
Insulation between thestuds must be tightly
fitted leaving no gaps
30 minute fireresistingproprietaryinsulating cavitybarrier withintegral DPC
Detail 3.08
Insulate the window reveal
Sealant to back of frame
Sealant at window frame
Weep Hole
Air tightness tape
Compressible fill
Use approved lintoldetails from timber
frame supplier
Vapour control layer
Cavity tray withminimum upstandof 140mm andstop ends
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Alternative internal finish at window
reveal - use insulation backedplasterboard
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/W
If position of window head islower than or level with theunderside of the lintol, a largercompressible filler will berequired to stop up a potentialair infiltration route
Timber FrameWindows and Doors - Jambs and Cills
Psi value (jamb)=0.0328W/mK Psi value (cill) = 0.0934W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier around opening
Air tightness checklist
1. Install window to overlap with outer leaf ofwall finish.
Alternative:If window lines through with the bottom ofthe opening in the external finish, somemeans of preventing a direct line of airinfiltration will be required
2. Install air tightness seal between theinside face of the window and thestructural finish of the window opening
Detail 3.09
Insulate the window reveal
Air tightness tape andsealant to back of frame
Sealant at window frame
30 minute fire resisting cavitybarrier with integral DPC
Vapour controllayer in wall
Insulation between thestuds must be tightly
fitted leaving no gaps
DPC lappedbehind cill andbelow window
Solid cill acts as cavitycloser. If pressed cill isused, a 30 minute firerated thermally insulatedcavity closer will berequied
Insulate the window reveal
Air tightness tape andsealant to back of frame
Compressiblefiller betweenwindow and cill
Vapour control layer in wall
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Alternative internal finish at window
reveal - use insulation backedplasterboard
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/W
Cill detail
Jamb detail
Timber FrameGround Bearing Floor: Insulation Above SlabPsi value = 0.1145W/mK
20mm strip of perimeterinsulation with thermal
conductivity (λ value) notexceeding 0.025 W/mK around
slab and any screed
Detail 3.10
Thermal continuity checklist
1. Use a lightweight loadbearing concreteblock where the wall abuts the concreteslab to minimise thermal bridging
2. Use a perimeter strip of insulation wherethe concrete slab abuts the concreteblockwork wall
Air tightness checklist
1. Ensure that any air tightness barrier usedin the wall overlaps onto the floor slab
External ground level
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Damp proof membraneabove or below slab
Vapour control layer belowtimber floor finish
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that concrete slab is level and
clear of debris before fitting the insulationat floor level
2. If a screed finish is used instead of a timber floor, use a strip of perimeter insulation with a minimum R value of 0.75 m²/KW for the depth of the screed
Alternative detail3. Using lightweight blockwork (e.g. with λ
value of 0.19W/mK) to improve thethermal performance at the junction wherethe external wall and ground floorconstructions meet will change the psivalue
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WFloor - 3.864(m²K)/W
Timber FrameGround Bearing Floor: Insulation Below SlabPsi value = 0.1733W/mK Detail 3.11
50mm strip of perimeterinsulation with thermal
conductivity (λ value) notexceeding 0.025 W/mK around
slab and any screed
Thermal continuity checklist
1. Use a lightweight loadbearing concreteblock where the wall abuts the concreteslab to minimise thermal bridging
2. Use a perimeter strip of insulation wherethe concrete slab abuts the concreteblockwork wall
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps onto the floor slab
External ground level
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Damp proof membrane
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. If a screed finish is used instead of a
timber floor, use a strip of perimeter insulation with a minimum R value of 0.75 m²/KW for the depth of the screed
Alternative detail2. Using lightweight blockwork (e.g. with λ
value of 0.19W/mK) to improve thethermal performance at the junctionwhere the external wall and ground floorconstructions meet will change the psivalue
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WFloor - 3.864(m²K)/W
Timber FrameTimber Suspended Ground FloorPsi value = 0.0423W/mK Detail 3.12
Sub floor ventilation should beprovided, minimum 1500mm²
per run of external wall or500mm² per m² of floor area
Thermal continuity checklist
1. Ensure that floor insulation butts againstthe insulation in the external wall
Air tightness checklist
1. Check that any air tightness barrier usedin the wall overlaps with the barrier in thefloor
External ground level
Add timber batten to cover the floor/wall junction. Useair tightness tape at junction of air barrier in wall and
floor. Seal between the wall and floor membrane with aflexible sealant or seal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Damp proof membrane
Air tightness barrier belowtimber floor finish
Insulation directly under flooringsupported on netting draped over
joists and stapled at required depths
Solum
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that all ventilation paths are clear
before installing the floor insulationAlternative detail2. Using lightweight blockwork (e.g.
with λ value of 0.19W/mK) to improvethermal performance at the junctionwhere the external wall and ground floorconstructions meet will change the psivalue
3. If there are concerns about damaging theair tightness membrane in the floor finishduring construction, an additional servicesvoid can be created using timber battenson top of the floor joists
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WFloor - 5.455(m²K)/W
Timber FrameSeparating WallPsi value = 0.0725W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier at junction of wall
Detail 3.13
Air tightness checklist
1. Check that any air tightness barrier usedin the internal wall overlaps with thebarrier in the external wall
Cavity barriers giving 30 minutefire resistance - ensure cavitybarriers are not breeched by
inappropriate insulation materialin the timber frame
For more information onacoustic details see
guidance in Section 5 ofthe Technical Standards
Vapour control layer in wall
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that insulation is fitted between
timber studs at corner junctions
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WInternal wall - 2.045(m²K)/W
Plan view
Timber FrameTimber Separating FloorPsi value = 0.0353W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier in line with floor
construction
Detail 3.14
Air tightness checklist
1. Check that any air tightness barrier usedin the external wall overlaps with thebarrier in the floor
Cavity barriergiving 30 minutefire resistance -ensure cavitybarrier is notbreeched byinappropriate rigidsheathinginsulation material Vapour control layer in wall
Cavityventilator
Insulation between the studs must betightly fitted leaving no gaps
Seal between the wall and floormembrane with a flexible sealant or sealthe gap between skirting board and floor
using a flexible sealant
Vapour control layer in wall
Separating floors to comply withSection 2: Fire and Section 5:
Noise
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that insulation is tightly fixed to the
timber studs adjacent to the floor junction,leaving no gaps
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/WFloor - 2.045(m²K)/W
Timber FrameIntermediate Floor / External WallPsi value = 0.0574W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier as necessary
Detail 3.15
Air tightness checklist
1. Check that any air tightness barrier usedin the external wall overlaps with thebarrier in the floor
Vapour control layer in wallInsulation between the
studs must be tightlyfitted, leaving no gaps
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that insulation is tightly fixed to the
timber studs adjacent to the floor junction,leaving no gaps
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/W
Install air tightness barrier aroundjoists, then lap membrane from
walls over it and tape junction
Timber FrameGround Floor/Separating Wall Junction- timber suspended floorPsi value = 0.0713W/mK
Thermal continuity checklist
1. Ensure that insulation is tightly fittedbetween the timber floor joists
2. Install cavity barrier as necessary
Detail 3.16
Air tightness checklist
1. Check that any air tightness barrier usedin the internal wall overlaps with thebarrier in the floor
Sub floor ventilation should beprovided, minimum 1500mm²
per run of external wall or500mm² per m² of floor area
Damp proof membrane
Use air tightness tape at junction of air barrier in walland floor. Seal between the wall and floor membrane
with a flexible sealant or seal the gap between skirtingboard and floor using a flexible sealant
Vapour contol layer in wall
Air tightness barrier belowtimber floor finish
Insulation directly under flooring -supported on netting draped over
joists and stapled at required depths
Solum
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that all ventilation paths are clear
before installing the floor insulationAlternative Detail2. Lightweight thermal blockwork can be
used in the separating wall to improve thethermal performance but this will alsoreduce the acoustic performance of thewall. If this alternative is used thenadditional elements will be required tomeet Section 5 of the TechnicalStandards.
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WFloor - 5.455(m²K)/W
Timber FrameConcrete Ground Floor/ Separating Wall: Insulation Below SlabPsi value = 0.2765W/mK
Thermal continuity checklist
1. Ensure that insulation is tightly fittedagainst the separating floor
Detail 3.17
Air tightness checklist
1. Check that any air tightness barrier usedin the internal wall overlaps onto the floorslab
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Damp proof membrane
Lightweight loadbearing concreteblockwork to minimise thermal bridging
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. If a screed finish is used instead of a
timber floor, use a strip of perimeter insulation with a minimum R value of 0.75 m²/KW for the depth of the screed
Alternative Detail2. Heavyweight thermal blockwork can be
used in the separating wall below slablevel but this will reduce the thermalperformance of this junction. Additionalconstruction elements may be requiredalong with lightweight blockwork in orderto meet the acoustic requirements ofSection 5 of the the Technical Standards
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WFloor - 3.864(m²K)/W
Timber FrameConcrete Ground Floor/ Separating Wall: Insulation Above SlabPsi value = 0.0146W/mK
Thermal continuity checklist
1. Ensure that insulation is tightly fittedagainst the separating floor
Detail 3.18
Air tightness checklist
1. Check that any air tightness barrier usedin the internal wall overlaps onto the floorslab
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Damp proof membrane
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that concrete slab is level and
clear of debris before fitting the insulationat floor level
2. If a screed finish is used instead of a timber floor, use a strip of perimeter insulation with a minimum R value of 0.75 m²/KW for the depth of the screed
Alternative Detail3. Lightweight thermal blockwork can be
used in the separating wall to improve thethermal performance but this will alsoreduce the acoustic performance of thewall. If this alternative is used thenadditional elements will be required tomeet Section 5 of the TechnicalStandards.
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WFloor - 3.864(m²K)/W
Seal air tightnessmembrane to floor slab
Vapour barrier in floor
Timber FrameSeparating Floor / Wall JunctionPsi value = 0.0241W/mK
Thermal continuity checklist
1. Ensure that insulation is tightly fitted
Detail 3.19
Air tightness checklist
1. Check that any air tightness barrierused in the internal wall overlaps withthe barrier in the floor
Alternative:Ensure that a continuous air tightnessbarrier from the wall wraps around theend of the floor construction, leavingno gaps
Vapour control layer in wall
Insulation between the studsmust be tightly fitted
Vapour control layer in ceiling
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Vapour control layer belowtimber floor finish
Separating floors requireadditional layers and components
to comply with Section 2: Fireand Section 5: Noise
Cavity barrier
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk
See general guidance notes
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WFloor - 2.045(m²K)/W
Timber FrameIntermediate FloorPsi value = 0.0333W/mK
Thermal continuity checklist
1. Ensure that insulation is tightly fitted
Detail 3.20
Vapour control layer in wall
Insulation between the studsmust be tightly fitted
Seal between the wall and floormembrane with a flexible sealant orseal the gap between skirting board
and floor using a flexible sealant
Vapour control layer in wall
Cavity barrier
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk s
See general guidance notes
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/W
Air tightness checklist
1. Check that any air tightness barrierused in the internal wall overlaps withthe barrier in the floor
Alternative:Ensure that a continuous air tightnessbarrier from the wall wraps around theend of the floor construction, leavingno gaps
Install air tightness barrier aroundjoists, then lap membrane from
walls over it and tape junction
Timber FramePitched Roof: Cold Roof / Separating Wall junctionPsi value = 0.0132W/mK
Thermal continuity checklist
1. Install a cavity barrier at the top of the wall2. Ensure that insulation layers in the roof are
fitted perpendicularly, to cover junctions
Air tightness checklist
1. Check that there are no gapsbetween the top of the masonry andthe underside of the roof
2. Check that the air tightness barrier inthe wall overlaps with the barrier inthe ceiling
Vapour control layer inwall and ceiling
Insulation between the studsmust be tightly fitted
Where two insulation typesare used together see
supplementary guidance
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.01 and 3.02 forother junctions using this roof construction
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Separating walls requireadditional layers and componentsto comply with Section 2: Fireand Section 5: Noise
Detail 3.21
Cavity barrier is used in line withceiling insulation to prevent thermalbypass.Use dense insulation orproprietary cavity barrier in sleeve
Timber FramePitched Roof: Ventilated Batten Void / Separating Wall JunctionPsi value = 0.0481W/mK Detail 3.22
Cavity barrier giving 30minute fire resistance -ensure cavity barrier is notbreeched by inappropriaterigid sheathing insulationmaterial
Vapour control layerin wall and ceiling
Insulation between the studsmust be tightly fitted
Where two insulation typesare used together see
supplementary guidance
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used indetails:
Internal Wall - 2.045 (m²K)/WRoof - 9.500(m²K)/W
Note: See detail numbers 3.03, 3.04 and 3.05for other junctions using this roof construction
Minimum 50mm ventilation path over insulation
Thermal continuity checklist
1. Install a cavity barrier at the top of the wall2. Ensure that insulation layers in the roof are
fitted perpendicularly, to cover junctions
Air tightness checklist
1. Check that there are no gapsbetween the top of the masonry andthe underside of the roof
2. Check that the air tightness barrier inthe wall overlaps with the barrier inthe ceiling
Separating walls requireadditional layers and componentsto comply with Section 2: Fireand Section 5: Noise
Note: this construction istypically used where thereare habitable rooms within
the roof construction
Timber FrameWall JunctionPsi value = 0.0179W/mK
Thermal continuity checklist
1. Check that there is no debris in the cavity2. Install cavity barrier
Detail 3.23
Air tightness checklist
1. Ensure that any air tightness barrier usedin the external wall overlaps at the corner
Plan view
Cavity barrier giving 30 minutefire resistance - ensure cavity
barrier is not breeched byinappropriate insulation
material
Insulation betweenthe studs must betightly fitted leavingno gaps
Vapour controllayer
HEAT 2.7 software image of isothermsthrough junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reductionof unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculationprovided the principles outlined and any identified component specification are followed.
Design advice
Minimising condensation risk1. Check that insulation is tightly fixed to
the timber studs at the corner junction,leaving no gaps
Thermal Resistance of insulation used indetails:
Wall - 3.182 (m²K)/WInsulated plasterboard - 1.591(m²K)/W
