We just had a meeting on insulation, heating, air conditioning, humidity control and air exchange for the new house.
Brian Uher came from Amicus Green, the place my architect, Peter VanderPoel, and I visited several months ago. He came over to meet with me; Peter; Ed Gill (my contractor); Ed’s assistant, Paul Walhout; and Peter’s assistant, Emily Johnson who just graduated with a degree in architecture from Howard.
It was so hot outside that we couldn’t meet in the soon-to-be-demolished house where all the utilities have been shut off already. So we decided to meet in my current home across the street where birds chirped loudly in their cage, cats prowled and dogs sniffed everyone indiscreetly. These people would see me in my natural habitat. Are all clients as quirky as I am? Anyway, I hoped this wouldn’t discourage Emily right at the beginning of her architectural career.
The first part of the meeting dealt with insulation. A lot of the discussion was technical, but I extracted from it that my house was going to be “tight.” If it were ever entirely shut up it would be like a screw top thermos bottle.
Early in the design process, we explored the idea of using prefabricated structural insulated panels (SIP). Precise measurements are sent to the manufacturer (and there are several dozen in the United States). When the custom built panels are delivered, they can be slipped into place and provide excellent support as well as excellent insulation to the new building. There is a house that was on the recent Arlington Green Home and Garden tour. Beforehand, I went to see it and took a picture of the finished product (see below). The trouble is, you can’t see the panels nor can you tell how it was built. So I went, naturally, to YouTube. If you want to see what I saw, just search using the keywords “Structural Insulated Panels.” It is inspiring, but we’re not using them.
Why not? Ed, Peter and Brian feel that we can get just as much insulation and structural benefit using traditional wood framing, caulking and insulation even underneath the basement foundation. The entire house will be wrapped in foam to eliminate all leaks. This process allows better fine-tuning of measurements than a prefabricated panel. And it is somewhat cheaper.
Then we talked about air exchange. Any tight house can allow nasty smells, carbon dioxide, moisture and toxic off-gassing from glues, carpets and paints to build up. This is what sick building syndrome is. To make sure this doesn’t happen, we need a controlled system of air exchange. About a third of the air in the home should be replaced every hour. So this is why we’re putting in an Energy Recovery Ventilation system of ducts that will form a simple trunk with short side branches. Outside air is warmed or cooled (as needed) before it enters the house by the discharged air. It also assists in dehumidification in the summer when moisture is most likely to be a problem.
We then began to talk about heating and cooling. Ductless mini-splits are going to give us summer cooling and winter heating. The process is not new; they use the same refrigerant heat pump technology that’s been around for a long time. It takes the heat out of the inside and moves it to the outside in summer and it does the reverse in the winter. It does not require a massive network of ducts with openings in the rooms for supply and return, however. Each unit can be independently controlled in case rooms are not in use. A cluster of units feed off of a single compressor that is outside and much smaller and more quiet than a big central air conditioning compressor. In my house I might need two or three of these clusters. When it’s moist, I might set the room units to simply dehumidify if I don’t need cooling.
What about geothermal? I had heard glowing reports of its cost efficiency. But early in the process of working with Amicus Green consultants, I was cured of any desire for it. The deep hole in the back yard where there might be a sensitive aquifer made me leery. And the very super efficiency of geothermal would be overkill in a house as small and as tight as mine will be. For maximum humidity control, it is better to have a system that is on most of the time rather than a highly efficient system that does its cooling fast and infrequent pulses.
The other technology that appeals to my uninformed instincts is radiant heating embedded in a concrete floor. I hear rooms that have hot water circulating underneath the floor are cozy and feel nice on bare feet. If I were to have this, I’d want it in the basement where the floors are likely to be clammy and where the heat generated can rise throughout the house. And the hot water could even be generated in rooftop collectors.
We talked at length about this and even mapped out ways that the pipes would flow and ways that water could be reheated as necessary. One of the disadvantages of this is that on bright sunny days, even in mid winter, the water will actually have to be chilled before it can circulate under our bare feet. Water temperatures can exceed 140 degrees and concrete is a very good conductor of heat. Ouch!
Brian stressed that if the basement floor is insulated underneath, there will be no clammy sensation in the first place. The ductless mini-split will be adequate. Then Ed said that just putting the tubes into the concrete is not that expensive and setting up the basement for the addition of a hydronic radiant system is not going to be hard to do in case some day I decide to install it.
Concrete floors in houses with large south-facing windows are a good way for gathering and retaining heat in the winter. This is known as “passive” solar heat. Until our meeting, Ed, Peter and I were taking for granted that we’d have concrete floors on the main level of the house where the floors are supported by soil and don’t have to be suspended over the basement.
But during the meeting we changed our minds about even this basic “green” idea. One big window opens on the east side where even wide eaves won’t screen the early morning sun and another big window opens on the west side where I’ll have the same problem in the late afternoon. Summers will make those rooms unbearable no matter how high we crank up our ductless mini splits. Besides, concrete tends to crack, gives fewer finishing choices and is more expensive than wood framed floors.
Before this meeting was over, we reluctantly severed our emotional ties with some of the appealing and trendy “green” technology in favor of more practical but equally efficient alternatives. The sexy new technology may earn gold and platinum points on someone’s “green” technology checklist, but it isn’t the answer to my problems. This process has been like going through a 12-step program to get off the knee-jerk addiction to green technology. Amicus Green is very experienced and has seen through some of the delusions that geothermal and passive solar have created in uniformed consumers like me.
Mary McCutcheon is a retired anthropology professor at George Mason University. This is her story of transforming her house from something she doesn’t want into something she does.