Energy performance should be a discussion in any home renovation where there is an opportunity to make improvements in energy consumption and improved comfort. While it should be part of the conversation, the outcome may be that additional insulation in a small sub-component of the home could actually be a bad thing to do.
Good building science works well when different components are assembled with synergy. In the 70’s during an energy crisis, insulation factors were significantly increased without simultaneously modifying the components it worked with. This resulted in premature exterior paint failure from vapor trapped in the structure, and required ventilation retrofits to make the system work “better”.
I have also seen the “green movement” in building science morph into a few camps based on ideology instead of a simpler health, and energy science. If you want to improve the energy performance of your home, start with increased insulation value while accounting for the rest of the building system. Second, change all the lighting in the home to LED. This will reduce excess heat in the summer and will reduce your electric bill right away with a short term payback. The third place to look is the heat plant. If you have older low efficient heating and cooling equipment, the change in efficiency from 80% to 94% will show up right away. Last but not least… if you are doing an entire exterior make-over… replace the windows. One at a time this doesn’t really change things. If you want to know what to do next… INSULATE MOREJ!
Here is a project we just completed in Wellesley. As part of a kitchen expansion, we did a complete exterior (and interior) make over. With blown in insulation in the budget along with all new windows, we discovered that a less effective insulation (about R9) had been installed by the last owner when they installed aluminum siding. We couldn’t get more insulation in the cavity so for the price of the blown in budget (about $5k) we suggested a one inch foam board to provide a thermal break. This pretty metallic red board does more than add 25-40% more to the insulation factor, but delivers a contiguous external thermal blanket that reduced hot and cold spots. This project with attic insulation and a new high efficient gas boiler shows the proof is in the pudding. Check out the comparison of last year’s energy report that came with the EverSource bill and the recent report!
The pictures of the home show the 3 phases of the exterior renovation (paint starts in a month or so).
Step one, strip to bare sheathing boards.
Step two, install a vapor barrier with 1” of foam board (they did finish the whole house… I showed up during that for the photo).
Step three, we sided with Hari Plank siding and Azek trim for a long lasting and beautiful low maintenance exterior that can be painted every 10-15 years.