Technical Installations in Passive Houses Part 1: Ventilation Systems

Ventilation Systems / 1 © Prof. Dr. Harald Krause

Technical Installations in Passive Houses

Part 1: Ventilation Systems

Prof. Dr. Harald Krause

www.btec-rosenheim.de www.fh-rosenheim.de

Århus 2007-08-29


Ventilation in Passive Houses

1. Indoor Air Quality and Ventilation

2. Cross Flow Ventilation in Dwellings

3. Components of a Ventilation System

4. Design of Ventilation Systems in Dwellings

5. Energy Saving with Heat Recovery


Indoor Air Quality and Ventilation Main Functions

Main Function: High Indoor Air Qualitypollutant concentrations

air humidity

Further Functions: Air ProcessingCleaning - Filtering

Heating (Cooling)

Dehumidification of indoor air

Energy Saving with Heat Recovery Systems


Indoor Air Quality and Ventilation Pollutants

Main Pollutants:

CO2

water vapour - humidity

odours

toxic gases

microorganisms

radioactive materials

Function of Ventilation Systems in Dwellings:

Keep concentration of pollutants and humidity as low as necessary

Extract odours

How to do this: supply fresh air, extract „polluted“ air


Indoor Air Quality and Ventilation Air Change Rate

Air Change Rate

Ve : air flow rate in m³/h

n: air change rate in h-1

Vroom: volume of the dwelling or room in m³

room

e

V

Vn

&=


Indoor Air Quality and Ventilation Max von Pettenkofer

Max von Pettenkofer (1858)

Use CO2 concentration as a benchmark for air quality


Indoor Air Quality and VentilationCO2-Concentration

CO2-concentration in indoor air

0,07 Vol.-%: recommended for occupied space

0,1 Vol.-%: Pettenkofer

0,15 Vol.-%: [DIN 1946-2]

0,5 Vol.-%: industrial-rooms

4,0 Vol.-%: exhale air

Caution: above 2,5 Vol.-% CO2 health risk


Indoor Air Quality and VentilationAir Flow Rate and CO2

0,06 0,08 0,10 0,12 0,14 [Vol%]

10

20

30

40

50

60

70

80

[m³/h]

100

air

flo

wra

te p

er p

erso

n

max. indoor CO2-concentration

CO2-emission per hour and person

sleeping (12 l/h)average (18 l/h)working (23 l/h)


Cross Flow Ventilation

Three Ventilation Zones

Supply “fresh” air to living, bed-, working rooms

Extract polluted, humid air from kitchen, WC etc.

supply air

• living

• sleeping

• children

• working

exhaust air

• kitchen

• bath

• WC

• utility

overflow

corridor


Cross Flow Ventilation Example

Example:

Zoning

exhaust air

supply air

overflow


air change rate 0,4 h-1, approx. 85 m² floor area

living25 m²

40 m³/h

bedroom16 m²

30 m³/h

children15 m²

20 m³/h

Supply Air

bath10 m²

30 m³/h

kitchen12 m²

60 m³/h

Exhaust Air

corr.8 m²

0,64 h-11,2 h-1

2 h-1

0,75 h-1

0,53 h-1

Cross Flow Ventilation Example


Components of a Ventilation System Overview

Balanced passivehouse ventilation:central ventilation unitseparated ducts for supply and exhaust airheat recoveryfiltering of outside airflow off vents

components:1. ventilation unit2. supply air outlet valve3. exhaust air inlet valve4. flow off vents5. air ducts6. outgoing air outlet7. outside air inlet

1

2 3

4

5

6

7


Filter

House

Air Ducts, e.g. ∅ 200mm

Condensate Outlet Device

Components of a Ventilation System Subsoil Heat Exchanger with Air


House

PE Ducts (water and frost protection liquid)

Outside Air

Water-to-Air Heat Exchanger

Components of a Ventilation System Subsoil Heat Exchanger with Water


Components of a Ventilation System Subsoil Heat Exchanger with Water or Air


Efficiency of heat recovery

85%

DC-motors

Air bypass for summer

Preheating of outside air for

frost protection

Balance of supply and exhaust

air flow rates

Components of a Ventilation System Central Unit - Example


Components :

Coarse filter G3 (1), fine filter F7 (2)

DC-fans (3)

Electrical preheating (4)

Bypass (5)

Heat recovery unit, counterflow heat

exchanger (6)

Condensate outlet (7)

Components of a Ventilation System Central Unit - Example


Components of a Ventilation System Air-to-Air Heat Exchanger – Heat Recovery

Efficiency of Heat Recovery:

Tzl: supply air temperature

Tal: outside air temperature

Ti: exhaust air temperatur (indoor air)

Example:

Tzl: 15 °C, Tal: 0 °C, Ti: 20°C

Φ = 75 %

Cross-Counter Flow

Cross Flow

ali

alzl

TT

TToder

−−

=Φη


Components of a Ventilation System Central Unit - Electrical Efficiency

Air Flow Rate in m³/h

elec

tric

alef

ficie

ncy

in W

h/m

³

External Pressure


Components of a Ventilation System Piping Systems

Material for Air Ducts

Zinc coated steel plate

Stainless steel, aluminium

Plastics (check, whether suitable for air, no emissions)

Types of Air Ducts

Round, folded spiral-seam tube (cheap, low air resitance)

Oval, folded spiral-seam tube (e.g. over suspended ceiling)

Plastics, (round, oval)

Flexible tubes (high air resistance, cleaning?)

Custom made

We recommend round folded spiral-seam tubes !


Components of a Ventilation System Piping Systems: Foulded Spiral-Seam Tubes

Sealing


Components of a Ventilation System Piping Systems: Oval Foulded Spiral-Seam Tubes


Components of a Ventilation System Thermal Insulation of Air Tubes

ref.: Drexel&Weiss


Components of a Ventilation System Exhaust Air Inlet Valve


Components of a Ventilation System Supply Air Outlet Valve

Wall Outlet

ref.: Drexel&Weiss

Blower Nozzle


Floor Outlet Floor Outlet

Ceiling Outlet

ref.: Drexel&Weiss

Components of a Ventilation System Supply Air Outlet Valve


Components of a Ventilation System Exhaust Air Outlet


Components of a Ventilation System Filters


ref.: Drexel&Weiss, Rehau

Components of a Ventilation SystemOutside Air Inlets


Components of a Ventilation SystemCondensate Outlet Devices for Subsoil Heat Exchangers

Condesate outlet device, if installed in basement


Components of a Ventilation SystemCondensate Outlet Devices for Subsoil Heat Exchangers

Pump shaft, if there is no basement


Components of a Ventilation SystemSubsoil Heat Exchanger with Water


Design of Ventilation Systems in Dwellings

Zoning: Supply, exhaust and overflow zones

Calculation of air flow rates

Take maximum of both air flow rates as design air flow rate

Divide up the air flow into the rooms of the supply air zone

Use the designed extract air flow rates for the rooms in theexhaust air zone

60 m³/h40 m³/h20 m³/h

Exhaust air flow rates:KitchenBath, utility etc.WC

30 m³/hSupply air flow rate per person


Basic rules:

Keep pressure loss as low as possible

Keep length of tubes as short as possible

Round tubes preferred

Dimensioning of ducts, in- and outlets

Chose a appropriate ducting system (round tubes preferred)

Positioning of in- and outles

Design sound absorbers (noise from central unit, air flow, between rooms)

Heat insulation of tubes

Positioning of outside air inlet (not polluted, driving rain protected, approx. 1,5 m above ground)

Dimensioning of subsoil heat exchanger (if needed)




ref.: Drexel&Weiss


Design of Ventilation Systems in DwellingsSubsoil Heat Exchangers with Air and Water

ref.: Drexel&Weiss

0.6 m per m³/h0.3 to 0.45 m per m³/hTube length

in combination withcompact heat pump unit

Frost Protection onlyAir Flow

Design guidlines: with Air

Design guidlines: with Water


Example:

Single family house with 4 inhabitants

1 kitchen, 2 bath rooms, 1 WC

150 m² floor area

Supply air: 4 x 30 m³/h = 120 m³/h

Extract air: 60 + 2 x 40 + 20 = 160 m³/h

Take maximum as design air flow rate: 160 m³/h

reduce this value with 0.77 as standard flow rate

Check mimimum air change rate in relation to hygienic

requirements:

160 m³/h / 150 m² x 2,5 m = 0,43 h-1

mimimum of 0,3 h-1 is complied



Energy Saving with Heat Recovery

EN 832: Influence of heat recovery on the annual heat demand

Calculation of the effective air exchange rate nL

nL = nsystem ⋅ ( 1 - ΦHR) + nL,inf

nsystem: average air change rate achieved through ventilation system

ΦHR: total heat recovery efficiency including subsoil heat exchanger

nL,Rest: infiltration air exchange rate caused by residual leakage throughthe airtight envelope

0,080,030,6

0,190,081,5

0,380,153

nL,Rest for heatingload in h-1

nL,inft for annualheat demand in h-1

n50-Wert

in h-1example: effective air exchangerates for a typ. single familyhouse, assuming average wind screening according to PHPP 2007


Energy Saving with Heat Recovery

Unit outside or inside

of the heat exchanging envelope

Keep outside air tubes in a warm room or supply airtubes in a cold room as short as possible !


Ventilation heat losses

Solar heat gains

Heat demand

Transmission heatlosses

Internal heat gains

Energy Saving with Heat RecoveryEnergy Balance


Energy Saving with Heat RecoveryEnergy Balance: Example for a Single Familiy House

15

9,7

21,3

40,6

22,215,9

1,0

0

10

20

30

40

50

60

70

Heat Gains Heat Losses

kW

h/m

²

Saving through subsoil HE

Saving through HR

Ventilation losses

Transmission losses

Solar heat gains

Internal heat gains

Annual heat demand


Example


Example


Example

Documents

Technical Installations in Passive Houses Part 1: Ventilation Systems