A Home’s Building Envelope and its Energy Efficiency

Posted by pcbasentry on March 10, 2009

Reprinted from HomeStars News and Updates

Tuesday, March 10, 2009

This is a guest post written by Debra Fenwick of Fenwick Design Group.

Note to readers of this blog: although this article was written in Canada, it contains some good information that can be applied anywhere.

Lately, the buzz in home renovation has been about the importance of the home’s building envelope and its effect on energy efficiency. The envelope is defined as the outer layer of the building that separates the living space from the outdoor environment both above and below grade. Creating a tighter envelope through upgrades and retrofits has been emphasized as one of the keys to lowering utility costs.

Building Envelope -- where heat escapes

Building Envelope — air flow

If we think of your home as an interactive system, many components come into play when calculating its energy rating, which in Canada is done using the Energuide Scale. A combination of the building envelope or structure, heating, ventilation and air conditioning, the external environment and the occupants themselves all add to the final result. But how do we find out how our home measures up and what are the best ways to improve its performance? What upgrades are the right ones for you and which ones will increase your energy savings while making sense from a budget perspective?

I sat down with the team from NEA (Nationwide Energy Advisors www.nwea.ca), a full service appraisal and energy audit firm whose self proclaimed goal is to “reduce Canada’s environmental footprint 1 home at a time”. The energy audit is the first step to increasing the energy efficiency of your home and getting a handle on where savings can be made. An initial 45 min-1 hour full analysis of your home is done (pricing starts @ $300 for a first visit, half of which can be recouped from the Ministry of Ontario) using testing procedures that vary from the “blower test”, to thermal imaging photography, tracer gas tests and basic questions about occupant comfort.

Building Envelope

Building Envelope

An energy model of the home is done using a specialized software system and recommendations made to the homeowner who then has an 18 month window to affect the upgrades. At this time, a second assessment is done and the audit company submits all of the applications for the available government grants. Reimbursements of up to $5000 from Natural Resources Canada and a similar amount from the Ontario Home Energy Savings Program can be expected 2-4 months after the completion of the 2nd audit.

So which upgrades will give you “the biggest bang for your buck”?

Michael White, Energy Program Director for NEA gave me his top five retrofits that produce the highest payback of dollars and energy efficiency

  1. Insulate your home’s foundation. Assuming the basement is currently uninsulated and there are no moisture problems this is often an overlooked area where heat loss occurs, is typically easy to get to, and not overly expensive to do.
  2. Replace old mechanical equipment with high efficiency models. Speaking to a licensed heating contractor to determine the right size of unit for your home is always a good idea. However, the sizing issue decreases in importance when dealing with high efficiency values. Traditional furnaces used to take a long time to heat up and then would shut off when totally boiled like a kettle so the amount of time in peak efficiency was low. The new high efficiency models take much less time to heat up therefore giving a steadier state of efficiency, their annual fuel utilization efficiency (AFUE) being 90-97% as compared to 60% for old furnaces or 78-84% for standard efficiency units. Also consider installing a programmable thermostat that allows you to preset your household temperature. Generally speaking, you can save 2% of your heating bill for every 1 degree you turn down the thermostat.
  3. Resolve air leakage issues by putting tight seals on doors and windows, caulking and sealing cracks or using expanding foam products to fill larger areas. Also pay attention to attic bypass leakage which are those airflows that cause the ice damming or icicles we see hanging from the roof lines around this time of year.
  4. Increase the insulation in your attic to a minimum of R-40
  5. Retrofit your main walls. Exterior walls are typically under insulated and when replacing siding or other external material the opportunity should be taken to add a minimum 2” layer of insulation under the new material.

As a runner up, Michael added the upgrade of doors and windows. This is an undertaking which, in some opinions, adds more to the value of your home from an aesthetic perspective than an energy saving one.

Effecting energy upgrades not only increases the comfort of your home and decreases your monthly bills. A push is being made by many in the industry to pass legislature currently known as the Home Energy Rating Act. It is meant to protect homeowners and tenants with mandatory home energy audits for all home sellers across Ontario. Home appraisers, real estate agents and the general public have finally become aware that the energy rating of a building should ultimately have an effect on its property value.

By taking small steps forward both on the individual and legislative fronts we will eventually reach a balance between home comfort and function, energy efficiency and environmental responsibility.

A small price to pay for a little research and action isn’t it?

Nationwide Energy Advisors will be at the Green Living Show in booth #2219 (April 23-26, 2009)

Debra Fenwick is an interior designer and LEED Accredited Professional working in the Toronto area . http://www.fenwickdesigngroup.com/


One Response to “A Home’s Building Envelope and its Energy Efficiency”

  1. Good advice. A good Home Performance contractor is the way to go. But regardless, keep a couple things in mind.

    Regarding the home energy audit, it’s important to get the right audit–accurate and actionable and looking at the right things like duct leakage, air infiltration, and equipment efficiency and safety and an analysis of utility bills. For a bit more background on audits and additional links, follow my post at http://greenhomesamerica.wordpress.com/2009/05/07/home-energy-audits-2/

    And be sure you choose a quality contractor. Things to look for are posted at http://greenhomesamerica.wordpress.com/2009/05/17/choosing-a-quality-contractor/

    Good luck!

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