Which energy efficiency upgrades are best for your house? That’s what an energy model will tell you.
How much insulation to use in the walls, the roof, or the floor are some of the most commonly asked questions in the construction industry – by both contractors and homeowners. Fluctuating energy prices, along with a jump in materials costs, underscores the importance of building a home that strikes a balance between energy efficiency and affordability.
In an ongoing effort to provide a prescriptive set of standards for the different regions of Alaska, the Alaska Housing Finance Corporation (AHFC) maintains the Building Energy Efficiency Standard. Any construction using AHFC-funded residential mortgage loans must comply with these standards. They also serve as a good reference for anyone considering building an energy efficient home in Alaska. Keep in mind that any construction that falls within municipal boundaries must also meet the local building code.
An energy model is the best way to gauge the impact of different levels of insulation (or any other energy efficiency upgrades) on your home. A computer modeling program runs a series of heat loss and performance calculations for every single component of the house. The dimensions and construction details of the exterior walls, roof, windows, foundation, and floor are entered into the program, along with specifics regarding the heating and electrical systems. What you end up with is a virtual model of your home. The program also contains the climate data needed to simulate your home’s performance in a particular part of the state.
Modeling is an incredibly useful tool because once all your information is entered, you can go back and change insulation values, construction types, heating appliances, and fuel prices to gauge your home’s performance under a variety of conditions.
First and foremost, the time to do the modeling is before you build, as you will retain the greatest degree of flexibility to make changes. Generally, the best approach is to hire a state-certified energy rater to enter your house plans into the program, which should cost between $350 to $700, depending on your house (other auditing services will cost more). If you are building using an AHFC-funded mortgage loan, then hiring a rater will be necessary in order to document compliance and to certify that the home meets AHFC standards.
If you want to try modeling yourself, a public version of the AK Warm program used in Alaska can be downloaded from the AHFC website.
Energy modeling is a powerful tool that can provide long-term savings and peace of mind with minimal up-front investment. You should realize, however, that occupant behaviors and awareness will also have a great impact on home performance. A house filled with teenagers and pets, for example, will perform differently than the same home inhabited by a retired couple.