positive pressure ventilation systems?
I need information on whole house ventilation systems that create a slight positive pressure in the living space by supplying filtered outside air. Everything I’ve found searching FHB use either balanced systems or negative pressure ventilation systems. <!—-><!—-> <!—->
The objective is to eliminate any crawl space air, attic space air, or unfiltered outside air from entering the living space due to stack effect, wind, vents and chimney, or whatever.<!—-> <!—->
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Background and previous remediations:<!—-><!—->
This house is a early 70’s 2K square foot single level rancher in north <!—-> <!—-><!—->Alabama<!—-> <!—->, built over a level crawl space with a poly vapor barrier over dirt. All walls and ceiling are drywall, and all windows are good old leaky double hung wood units. (replacing the windows is not an option)
The HVAC is forced air heat pump. All ductwork seams, joints, and connectors are sealed with mastic and mastic tape. All supply ducts are R-8 with R-6 being the local code. The return ducts are R-6. Two bath vents, one stove vent, and a chimney.
Indoor RH runs 55% to 60% in the middle of summer.<!—-> <!—->
I have caulked and gasketed all electrical boxes, foamed all plumbing openings I can access, and caulked the perimeter of all rooms at the intersection of subfloor and drywall when we changed carpet over to hardwood and tile.
These sealing measures greatly reduced the wife’s hyper allergies, but unfiltered outside air is still an issue and we may be closer to sick house syndrome due to stale air.<!—-> <!—->
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Does anyone have experience with a filtered positive pressure system? I’d prefer to splice into the existing HVAC if possible. Any details or suggestions are appreciated.<!—-><!—->
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Thanks,<!—-> <!—->
Glenn <!—-> <!—->
Replies
http://www.aircycler.com/how.htm
The air cycler seems to be the state of the art on these things. I'd make sure you have your crawl sealed up well first before I invested in the air cycler though. But you may want to do both. Have you enlisted the help of an energy star audit with blower door and duct blaster? it may be that you have a drafty HVAC cabinet sucking air from your crawl into your home combined with a high humidity in the crawl.
m
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"You cannot work hard enough to make up for a sloppy estimate."
Aprilair makes a device I am considering for my home. You can control the cycles and it does not operate if bringing in outside air changes the humidity making it to high in the house. From what I can tell it has censors that are inside the house and outside. I think you mentioned you live in a Ranch. You could access all exhaust fans and change them to a Central unit. Then put an air to air heat exchanger in that system bringing in filtered fresh air when you are exhausting stale air. I can't do that I have a two story. The American Lung Society on their web site has suggestions about fresh air make up that is best for the occupants. Hope this helps a little. Jay
Most newer apartment buildings and condo complexes have a positive air system. This positive air is usually blown into the hallways which keeps the cooking smells from each unit from coming into the hallways. These fans run continuosly and in the winetr there is usually a resistance heater which heats up the air somewhat as it comes in.
These fans can only pump in only so much air to give it a very slight positive pressure and it helps cold air fromcoming into the building so I was taught. Air can only be pumped into a building at the same rate it leaves. Like anything else, when it's full, it's full.
roger
I have a 6" inline (185 cfm) fan tied into my return air before the filters. It's wired into the furnace & only comes on when the fan is running, in either heating or cooling mode.
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