Tight Efficient Houses

[mainemac]

Nice Link on Heat Exchanger from NY Times for those interested.
Most of us already have homes but for those thinking of building .....

http://www.nytimes.com/interactive/...sinessofgreen_house.html?ref=businessspecial2

1) This heat exchanger sounds like it violates conservation of energy like a perpetual motion machine somehow it spins and sucks heat out of the air??
2) OK anyone else tired about hearing how much better other countries are at energy efficiency?
When I was growing up we were putting men on the moon. Now all our houses even in cold Northern states are built with lazy 'routine' insulation and designs from the 60s when oil was 25 cents a gallon. (making em bigger but less efficient kinda like our cars)

Tom

 

[madrone]

It's funny how simple and inexpensive most of these things are. Passive heat, (the slab floor, awnings, house orientation,) don't really add to the cost, but have a huge impact. If I were building a house, there's no good reason not to do as much of this stuff as you can.

The exchanger is pretty cool. There's no way it recaptures all the heat of the exhaust air, but it's reducing the loss.

 

[North of 60]

All commercial and institutional buildings here that require 100% fresh air makeup use the heat wheel design. Most houses use the air to air paper or aluminum design heat exchanger for new code installs. They require a defrost cycle or a source of preheat in front of them due to plugging up with ice in extreme cold temps @ -20c and below for them to work efficiently. This is caused by the warm moist air that is being exhausted from the building to condense on the exchanger from the cold outside air passing on the opposite side of the exchanger. Some installs will also have a reheat after the unit to bump the supply air temp back up to rid the cooling effect they can cause. The exchange will never be 1to1 but sure help on recovering some heat before being exhausted. They are known as HRVs. Heat Recovery Ventilator's.
N of 60

 

[EatenByLimestone]

I think you'll find that gas at 25c/gallon was more expensive than it is now when you consider most people made about $5000/yr.


Matt

 

[SolarAndWood]

I am kind of surprised by the wall to roof insulation ratio. 12" walls and only 16" roof? It seems that the budget would be better spent on more roof insulation and a way to conveniently reduce heat loss through the windows.

Also, can you reasonably expect to produce enough electricity on site to run a heat exchanger? If you have the inclination and are set up properly, wood seems to be a far better source of heat than electricity. It also stores better. The batteries in my coming PV system would buy a lot of firewood and they certainly wouldn't keep the house warm for very long without charging.

 

[begreen]

I'm excited that these systems are finally starting to meet the main stream. In 1983-4 I designed systems for a large new photo lab. Part of the systems design was a very large (about 4'x8') air-to-air heat exchanger that used the low boiling point of freon to transfer the heat from the exhaust air, to the incoming fresh air. The 17,000 sq ft facility changed its air about once an hour and heated itself mostly from the waste heat that the processors generated. Only when it got below about 25 did the heat come on in the morning to warm up the building. And this was in a 1920's building retrofit. It was the only photo lab I've been in that didn't smell like one.

Big photo processors use a lot of hot water. I did the same thing with that consumption, but there the savings were much more dramatic. Incoming cold city water was passed through a heat exchanger and preheated by the waste warm water coming out of the processors. This was a new facility so I could design the drain system so that it isolated the warm processor water from cold water waste systems. The result was that it cut down natural gas hot water heaters energy consumption to about 1/4 the predicted load for the facility by the gas company. A bit intimidated by the gas co's recommendations, I predicted a 5 yr. payback period for this system and quite honestly was pretty anxious that there would be enough hot water. There was, and the system paid itself off in less than a year.

We can do so much better right now and don't need to wait for future technology. But it takes the will and vision to think smarter, designing better systems and buildings with the tools and technology we have at hand. My hat is off to the folks leading this movement.