By Tod King, MBA
Design/construction professionals working on single-family residential projects are facing diametrically opposing forces––the need for energy efficiency, environmentally sensitive construction, and macroeconomic demand for lower construction costs. As specifiers aspire toward a ‘net-zero-energy’ home (See Natural Resources Canada’s (NRCan’s) “Net-zero-energy Housing: Design in Harmony with the Environment,” by Emmanuelle Brière, in Natural Elements. Visit www.nrcan.gc.ca/com/elements/issues/39/netzero-eng.php). with a price tag currently out of reach for most Canadians, this author discusses what can realistically be achieved at an affordable price for a typical Canadian home.
This article looks at insulation material choices available today when specifying and building a new home in Canada. Providing an analysis of the trade-offs each material affords, it proposes a pragmatic hybrid solution that balances the lowest first cost against the total cost of ownership.
One should consider a common scenario in home design, which typically starts at the drafting table with the architect or new home designer faced with a plethora of energy efficiency decisions. One should assume the required building standard has been selected, whether simply to comply with the minimum provincial standards, or the higher R-2000 Energy Star for New Homes (ESNH) or new EnerGuide Rating System (ERS) standards. (For more information, see NRCan’s “What is the EnerGuide Rating Service?” online at oee.nrcan.gc.ca/residential/builders-renovators-trades/15657).
It is important to consider the ‘house as a system’––individual components contribute to the overall performance. (See NRCan’s “The House as a System.” Visit oee.nrcan.gc.ca/residential/new-homes/upgrade-packages/3438). In this context, one starts to consider how to achieve the required R-values for the various components of the building envelope, such as exterior walls, attics, ceilings, and foundations.
Photos courtesy Kinlar
More enlightened home designers understand R-value is only a basic calculation of heat flux in samples of various types of insulation material calculated or measured under perfect laboratory conditions. Unfortunately, these methods have shortcomings when compared to the actual conditions of the materials when subjected to a home in a typical Canadian climate.
There are six important mechanisms for conduction through a wall or ceiling:
- conduction;
- radiation;
- convection currents;
- infiltration (i.e. wind pressure);
- intrusion (i.e. wind wash); and
- moisture accumulation (i.e. humidity, dew, and frost). (For more information, see Spray Polyurethane Foam Alliance’s (SPFA’s) “Applications of Spray Polyurethane Foam–Residential Applications: Six Mechanisms of Heat Loss Through a Wall or Ceiling That Are Bad for Your Home and Your Health.” Visit www.sprayfoam.org/index.php?page_id=198#residential).
Little or no allowance is made to the latter mechanisms. Fibreglass batts, for example, are tested under ASTM C 653, Standard Guide for the Determination of Thermal Resistance of Low-density Blanket-type Mineral Fibre Insulation, at 23.9 C (75 F). (See ASTM C 653-97 (2007), Standard Guide for Determination of the Thermal Resistance of Low-density Blanket-type Mineral Fibre Insulation).
Potential with sprayfoam
In short, if one insulates a building with material featuring high theoretical R-value, one may also want to question how effective that material will be when subjected to air loss, moisture retention, or having been poorly fitted into stud cavities, around electrical fittings or plumbing, or together with seams.
Closed-cell sprayed polyurethane foam (ccSPF) insulation, which is tested to the rigorous ASTM C 1029, Standard Specification for Spray-applied Rigid Cellular Polyurethane Thermal Insulation, (See ASTM C 1029, Standard Specification for Spray-applied Rigid Cellular Polyurethane Thermal Insulation). and field-proven to provide a significantly superior installed R-value over the property’s entire lifetime, under a wider range of environmental conditions, can be a suitable choice.
In the past, a permit could be issued confirming a home had been constructed with the desired R-value complying with code specifications, using traditional insulation materials, but without actually delivering the desired performance necessary to achieve true energy efficiency because the finished home leaked air and lost heating/cooling via the mentioned conduction mechanisms. In recognition of this, the newer energy efficiency standards––such as EnerGuide––require new homes be independently evaluated by an energy advisor, including a blower door test assessment of air leakage.
While many home designers and builders focus on insulation details such as ensuring the vapour barrier is properly installed and sealed, the concept of an air barrier is often overlooked. Since new homes are required to have air exchangers or heat recovery units to comply with the National Building Code of Canada (NBC), it is practical and achievable to air-seal a home. Many builders now take this approach, which is a key enabler for energy efficiency, and it is more likely to ensure the property passes the new blower door test.
In simple terms, which would a new homeowner choose––would they prefer a high R-value drafty home or an air-sealed home with same R-value, but with lower energy costs due to better performance?
Economics lesson
The issue of performance superiority of ccSPF versus other forms of insulation material is well-documented. However, closed-cell sprayfoam can only be installed by a Canadian Urethane Foam Contractors Association (CUFCA)-approved contractor, which is both an advantage and a disadvantage. The most significant drawback of ccSPF is upfront cost and the impact on the total new home price point for the home buyer. Most buyers give more consideration to the cosmetic features of a new home and focus on tangible upgrades such as hardwood floors, granite countertops, and kitchen islands.
In general, ccSPF can cost two to three times the ‘on-the-shelf’ price of other traditional forms of insulation––not including installation, vapour barrier, and sealant. One must factor in the lifetime return on investment (ROI) on ccSPF, with 30 to 40 per cent better energy efficiency and structure rigidity. Additional long-term benefits of ccSPF include:
- structure durability;
- protection from wood rot;
- noise reduction; and
- better interior air quality (IAQ).
According to Statistics Canada, in 2007, Canadians spent an average $1757 per household annually on electricity and natural gas (For more information, see the average energy cost per household from Statistics Canada’s “Households and the Environment: Energy Use.” Visit www.statcan.gc.ca/pub/11-526-s/2010001/part-partie1-eng.htm).––predominantly heating and cooling their homes. This data predates large increases in energy costs, particularly electricity, and the introduction of an additional eight per cent provincial element of the harmonized sales tax (HST) on home energy in Ontario.
