Air exchanger - ralst

ralst

Currently building slab on grade with radiant infloor heat. Will be installing an air to air exchanger and thinking of running duct work under slab and up through walls for exhaust and fresh air vents as opposed to through trusses and then down. My thoughts are, less holes through vapour barrier in ceiling and hopefully easier installation, ie no insulating of ducts etc. and incoming cold air has more chance to "warm up" prior to being Extremely cold climate.

Any thoughts on this? Thanks, Bob

don_9

Fresh air

Ralst or we talking about fresh air ventilation.honey well has a hrv that has a heat transfer core that recover
up to 85% of spent air. At only 200 cfm for most home should
not be to much of a issue to add to load.you can used pvc pipe for distribution. I dont get to see many basement in this area or they that tight that you have to introduce
fresh air? don

Mike T., Swampeast MO

An old Popular Mechanics...

...had something similar. Home with basement in New England. Standard concrete blocks were dry laid so that the holes lined up end-to-end. This was done over a deep gravel bed with thick plastic and more gravel over the top. Basement floor poured on top.

This became, in effect, a constant temp/constant flow air exchange system. Owner-designed & engineered. Fairly large home with a lot of glass heated with a wood stove and massive central stone chimney. Extremely small amount of wood burned and little/no use of A/C. Supposedly, interior temp didn't vary more than a degree or two over an entire year.

I would imagine that something similar could be done with an HRV/ERV at little added cost. If you make the air path sufficiently wide (use 6-8 blocks?) and/or long (go from one end of the slab to the other with fewer blocks) there would definitely be some air tempering going on.

Dale

I would not go in the floor

for this application, the heat exchangers move alot of volume and I would be concerned with moisture condensation and the cleaning options with a poured floor duct system. One possibility is to make the attic part of the insulated area, you'll need exhaust vents from the baths and kitchen anyway. I'm seeing this done more and more in ultra hot climates and it might be the answer for all slab on grade houses. For a manufacturers opinion on the AAHX floor duct run contact Research Products corp which makes the "Perfect Air" system. Phone 608-257-8801. You are wise to go with an AAHX, CO2 levels and moilsture levels in modern insulated houses are not heathy IMHO.

Eric

ductwork

Running cold outside air in duct in wall is bad idea.

Air will cool wall just as much as wall will warm air.

In alaska we always keep outside air duct as short as possible, Keep it well insulated with a good vapor barrier on duct to prevent frosting.

j_4

under slab ducts buried in concrete are a pain in the....

-adds cost to the concrete work
-ducts should be coated steel or plastic (check out www.spunstrand.com for add'l info)
-ducts should be anchored or else they tend to float up when you pour
-SMACNA says to brace internally and do it in 3 pours to prevent collapse due to concrete weight
-insulate the hell out of them and seal for a completely water & air tight vapor barrier
-slope to drain
-hopr you don;t get a laek & grow mold inside