Air sealing and Negative Pressures

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  #1  
Old 04-09-10, 06:09 PM
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Air sealing and Negative Pressures

I have been at the house for a while now on air sealing to provide savings and more comfort for the family. I sealed what I could in the attic, and started to seal in the basement. One thing I am finding when using an inscense stick is the amount of air that it being drawn from the living space (1st Floor) into the basement is ungodly. We have some areas in our home where there are opening in the walls, some small and others large where the plaster is missing and needs repaired. I know this is acounting for alot of heat loss. Where I am concerned is we heat with a wood furnace. When I reducted the house a few years ago I didn't put any supplys or returns in the basement because I didn't want any negative pressure due to the wood furnace. I assume its a negative pressure issue. If I could neutralize the pressure in the basement, would the heated air from the living space still feed into the basement? Being a balloon frame home, its very difficult to trace all patterns of the air. I also thought about blowing cellouse into the interior walls from the attic, but didn't know if it would help since the cavities are capped and sealed. I understand that any loss of air on a dwelling will allow for air to enter. There still are a ton of air leaks entering the home and I can't figure where else air would be leaking from the home. Any thoughts or ideas? Thanks
 
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  #2  
Old 04-10-10, 10:35 AM
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First homes need 60 to 80 cfm for good IAQ. 2nd your stove or the HVAC system is causing your negative pressure in the basement. Do you have any duct that is in a non conditioned space?
 
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Old 04-10-10, 02:34 PM
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Our basement is unfinished. Its a dungeon so we just store stuff there. Almost all the ductwork is in the basement which is unheated, but stays 60 or more with the radiant heat of the woodfurnace. The woodfurnace's ductwork is sealed and so is all the other ductwork. There are no heat ducts or returns in the basement. What I am figuring is we are losing alot of heat in the living space due to the air being drawn from the living space into the basement. I capped the base of all the interior walls in the basement, or tried to seal them to stop air movement in interior walls of the house.
 
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Old 04-10-10, 04:14 PM
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With balloon construction, there is a path from basement to attic that is stealing your basement air. The replacement air is then being pulled from the first floor into the basement.

Use an insense stick or other mild smoke source to see if you can locate leaks. How did you seal all of the balloon cavities and did you get them all? Any gap around the chimney or plumbing pipes? How about bath tubs, sinks, and showers.

When you say your ducts are sealed, are you saying all seams have been taped or sealed with duct mastic? Where is the blower for your air circulation? Any leaks there will result in an imbalance of air pressure.

Bottom line, if air is flowing down into the basement, there has to be air leaving somewhere. Find and stop that and the air will no longer be pulled down.

My only other concern is combustion air. Where is the wood burner drawing its combustion air. If you aren't providing a supply, then perhaps that is the leak, and that is not good.

Bud
 
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Old 04-10-10, 04:51 PM
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I sealed the cavities in the attic with aluminum sheets and fireproof caulk. I thought I got all of them, but maybe not. Its hard when there is insulation up there already. The ducts were sealed with foil backed tape, which were cleaned off well before applying. The chimney is an exterior chimney. Will any holes on the exterior of the home cause this issue? The corners of the home look like there is possibly some locations for leaks, on top of holes that birds and bees have put into the ginerbread moulding on the outside of the home. The blower is built into the woodfurnace, just like a gas furnace is. It doesn't have a seperate source of combustion air, just the basement. Even with the woodfurnace not running, there still is air coming into the basement. I want to hire a energy auditor, but can't afford to. I know somewhere in this home there is a major leak(s) and I can't figure it out. If I needed a fresh air intake for the basement, I'm afraid it will pull too much cold air into the house, and act like a huge leak. One thing I forgot to add, I was able to seal one side of the base of the interior walls in the basement, but the otherside is strictly flooring and or I can't get to the other side. I'm not sure if it was good enough. I do know that every notch for the joist in the beam is an opening to the wall. Whats the easiest way to remove the cellouse in the attic so I can look over everything?
 
  #6  
Old 04-10-10, 05:26 PM
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I just did an experiment. I took an insense stick and placed it in the areas where the air was pouring into the basement. The smoke moved away from the openings, but when the fan only was turned on then there was an instant pull of air into the basement at a good pace. If I can stop this will it make a difference on how the house will feel or heat? I guess its one way to find openings from the living space to basement, but I didn't realize it was being caused by the hvac. How can I remedy this and why is it doing this?
 
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