What is a Deep Energy Retrofit?
DERs are basically a combination plan of attack to improve a home's energy efficiency. We approach DERs from 2 directions:
- Getting the envelope of the house much more insulated /air tight AND
- Installing more efficient HVAC systems, water heaters, appliances, light bulbs etc.
The envelope of the house refers to the roof, walls, basement(or crawlspace or slab-on-grade), windows and exterior doors . We improve the envelope by:
Adding insulation. Adding insulation to an attic is generally easy. Often the basement is easy to fix as well. (You just have to make sure you have addressed moisture infiltration first and know that there will be tough spots where utilities are entering and existing.) Walls are a bit tougher as you have to remove sheet rock OR remove siding to really insulate them well. You can blow in insulation vie small holes in the tops and bottom of walls...but if you are re-siding your house anyway- don't miss the opportunity to add insulation!
Killing air infiltration. Air infiltration greatly reduces the effectiveness of your insulation and is also the culprit when it comes to mold, mildew, water damage and just plain old drafts. All of which also bring microscopic bugs, tiny critters and other vermin into your house. Blech.
Replacing windows and glass doors or at least fixing the weather stripping and caulking around all exterior opening. Replacing doors and windows can be quite expensive. Some people in the green world do not think it has a good enough ROI (return on investment). I often disagree. Windows are one of those things that completely upgrade the look and quality of a house. So if your house needs a face-lift or of you need a hammer to open or close your double hungs, if you are sick of storm windows AND your windows are freezing. The I would go for it. (Assuming funds are available.) They kill a lot of birds with one stone. (ooh bad analogy.... birds... windows... Poor little birdies. )
The overall theory is that if you make your house more efficient by adding insulation to the walls, roof, basement and installing better windows and preventing air and moisture leaks then you will need a much smaller HVAC system to heat and cool the home. So if you do the envelope first you will spend a LOT less money than you would have on that new efficient HVAC system. No matter what your fuel source- you will use less of it.
The theory behind the Passive House movement is that if you get the house SUPER insulated- like 'to the max' then you will need almost no heating and cooling system. You definitely need a ventilation system in this case but you can truly get away with a couple of small space heaters. If you need AC then you can get a wall mounted mini-split heat pump system that will heat and cool the whole house for peanuts.
You do not have to do both the envelope and the HVAC system together. It is ideal if you do – but you don’t HAVE to. In our world we do encourage people to address the envelope insulation and air leaks first. HVAC comes second because you often get more bang for your buck doing the envelope- but again you do not have to do it that way and it does depend on the house.
Good luck and please call if you need more info!