Quality Information for Energy Conservation

The Whole House Approach

Posted in: HERS Raters

We sat down and interviewed one of our Raters, Roy Chatalbash, and got his view on what he calls the Whole House approach to HERS Rating. 

SEA: What does energy rating mean to you?

Roy: The Home Energy Rating System (HERS) methodology takes into consideration a large group of variables that help a Rater understand the relative performance of the different attributes of a home, and enables the Rater to compare one house with another.  For example, a home that has more window area than an average home may need to have a larger HVAC system to provide adequate comfort. So, one consequence of a possible design decision, more glazing (windows), creates higher energy use and therefore a negative effect on the HERS Index.

SEA: When you say a whole house approach, what does that mean for energy rating?

Roy: Using the example above, the consequence of a design decision created an energy penalty. Therefore, I believe it should be a Rater’s job during the design phase to discuss the energy implications of a particular design decision. That highlights key decision-points early enough so changes can be made before the home is built.

SEA: Design decision implications such as…

Roy: Everything in the house impacts something else.  CFL’s give off less heat which is great for cooling in the summer (more lights no longer means more heat) but in the winter you’ll notice that as well; more windows for aesthetic reasons means there is less insulation around the exterior, hence more heating and cooling is needed to maintain a “normal” temp.

SEA: Is there such a thing as “too tight”? 

Roy: I hear this from builders a lot. The answer is definitively, NO! What builder’s fear is that a tight house will trap moisture and eventually rot the framing because it doesn’t have a path to dry.  In addition, they’re worried that there isn’t adequate fresh air for the occupants.

Air is a notoriously difficult thing to block.  An air barrier has to be durable, complete and aligned to work effectively. If it’s installed correctly, then there won’t be vapor-laden air that infiltrates the building shell to create the environment for mold. And, the typically small amount of vapor that diffuses into the assembly has the ability to dry to the outside in our climate zone.

It is true that trapping air also means poorer air quality. To address it, mechanical ventilation is required; bath fans are most commonly used for this.  The idea is to exhaust only enough air that is necessary for the health of the occupants so that the home provides a healthy environment and is energy-efficient.

SEA: If I don’t have an energy rating but I know I need to do something – where should I start? Do I have to do everything at once?

Roy: Like so many decisions, the best way to start is with a well-thought through plan. If budget constraints require phasing energy-related upgrades over time, then the plan ought to include the highest priorities first, which is typically air-sealing and insulation improvements. There are free assessments services available through MassSave, but the advice tends to be one-size-fits all instead of a tailored review. At SEA, using the whole-house approach, we use many diagnostic tools to determine the right course of action.

 

Stay tuned for more interviews with our Team and if you have an interview topic, let us know in the comments!