A note to presenters:1. This presentation contains extra notes about each slide including

background and supplemental information. These are accessible by changing the view to “Notes Page” which is done under the “View” tab in the main toolbar.

2. This presentation can be accompanied by a handout, available for download on CCHRC’s thermal mass webpage: http://www.cchrc.org/thermal-mass-study They both summarize research conducted at CCHRC from 2013 to 2014.

Promoting and advancing the development of healthy, durable, and sustainable shelter for

Alaskans and other circumpolar people .

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rCCHRC Building Science Research

The Effect of Thermal Mass on Annual Heat Load and Thermal Comfort in Cold Climate Construction

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rIn other words:

1. What is thermal mass?

2. Why study thermal mass?

3. How to study thermal mass?

4. Energy modeling

5. Effect of thermal mass on annual heat load

6. Effect of thermal mass on occupant comfort

7. Context

8. Practical applications

9. What is next?

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rWhat is thermal mass?

There is mass (see image below) and then there is thermal mass.

In construction, thermal mass refers to dense, heavy materials with a high heat storage capacity. What are some of these materials?

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rSome examples of thermal mass in Alaska construction are:

Log walls, Concrete, Masonry, Stone, Adobe

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rDistinction: Thermal mass is one part of thermal storage systems.

Thermal mass, in our context, does not have a dedicated control system.

Thermal storage heating systems use thermal mass as a heat “battery.” They are distinct from thermal mass in the envelope because they contain a dedicated control system that activates heat collection and distribution.

For example, a solar thermal system in Alaska might store heat in a tank of water during the day for use heating a home at night.

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rDistinction: Thermal mass is part of passive solar systems.

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rWhy study thermal mass in cold climate construction?

In this study, we look at thermal mass in a building envelope in a typical residence (no attention to passive solar design) to see if it has benefits in a cold climate.

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rVideo recap!

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rHow did we study thermal mass in cold climate construction?

In this study, we used the energy modeling software IDA Indoor Climate and Environment (IDA ICE) to simulate the thermal mass in a home.

• Control over external parameters such as residences, heating systems, weather

• Same residence in different locations

• Time savings over doing an experimental study

• Ability to use a control location to test the model – in this study, New Mexico’s mixed climate served as a control

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rFirst, a look at other research.

Before we began the modeling, we looked to other research studies to establish some background on thermal mass in building envelopes.

• Many modeling and experimental studies have documented that increased thermal mass can lower annual heat demand in a mixed climate.

We expect to see the same with our model in the Clayton, NM location.

• In cold climates, the research was less established though two studies found that the effect of increased thermal mass was small in Nordic climates.

Can we extend these results to Alaska’s cold climate?

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rA model house

The model was created using average characteristics of Alaskan homes in the ARIS database that met BEES 2006-2012.

It is a typical house with no particular attention to passive solar design.

Floor area 2,000 ft2(ground area 1,000 ft2)

Total window area 180 ft2

Window/Envelope 4.20%

R-value of walls 20

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rAnd its characteristics…

Two cooling zones, with an ideal cooler with a set point of 81°F. Windows were programmed to open at 77°F.

Constant internal gains of 150 W and additional internal gains for cooking (1500 W) and entertainment (200 W) which were ON for 2 hours each day

Two heating zones with an ideal heater to provide heat. Temperature set point was 68°F for the heating season and 60°F for the cooling season.

Four residents occupied the house. During the week, the house was empty during working hours.

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rLocation, location, location

Location

Clayton, NM Zone 4

Juneau, AK Zone 7

Fairbanks, AK Zone 8

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rSimulations

FloorLightweight floorHeavy floorAdditional 4 inches of concrete on first floor, and 2 inches of concrete on second floor

Walls (all with identical R-value of 20)

8 inch ICF wall

19 inch log wall

5.8 inch framed wall with dense-pack cellulose insulation

6.7 inch framed wall with fiberglass insulation

3.1 inch concrete interior, 4.8 inch thermal insulation exterior

8 inch concrete interior, 4.7 inch thermal insulation exterior

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rVideo recap and preview!

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rEffect of thermal mass on annual heat load

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rZooming in…

Light Heavy Light Heavy Light Heavy0

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11.48 11.13

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Fairbanks: 2% difference

Juneau: 3% difference

Clayton: 25% difference

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rHeat flow matters!

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rEffect of thermal mass on occupant comfort - spring

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rEffect of thermal mass on occupant comfort - summer

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rIn summary…

Reduction in annual heating demand for Clayton, NM was in agreement with other studies – Clayton served as approximate verification of the energy model.

In all climates, added thermal mass increased occupant comfort. In all climates, added thermal mass did not increase the annual heating demand.

In cold climates, the added thermal mass did not have a large effect on the heating load of the house.

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rContext

• “Typical” residential building

• Ideal heating system with two zones (upstairs and downstairs)

• Small internal gains

• Thermal mass on the interior of the building

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rPractical applications for cold climates

Thermal mass has benefits in all climates, including cold climates. However, if you want to reduce the fuel use of a residence, other strategies such as adding insulation in the building envelope, making the envelope air-tight, and using an efficient heating appliance will have a bigger effect than incorporating additional thermal mass.

R-22 Light Wall R-22 Heavy Wall R-29 Light Wall R-29 Heavy Wall0

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Energy model of typical house in Fairbanks, AK

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rWhat is next?

Improved model: different house design, a passive solar design, super-insulated structure, commercial building, non-ideal heater…Preliminary modeling has indicated that in some of these cases, thermal mass in the envelope might be more beneficial than in a typical Alaskan residence.

Survey of existing homes: Rather than a modeling study where all variables are controlled, such a survey would look for trends related to thermal mass in a large number of existing homes.

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rThanks!

Acknowledgements: Alaska Housing Finance Corporation

Research Team: Martin Kotol (Technical University of Denmark)Vanessa Stevens, Colin Craven, Bruno Grunau (CCHRC)

Contact:Vanessa Stevens (vanessa@cchrc.org )

More information: www.cchrc.org