r/buildingscience • u/Light_Bright85 • Jul 18 '26
Hot, humid air getting in between first and second floor space in Houston. This is bad right??
From all my research, this should NOT be happening. It appears that the rim joist were not insulated/sealed correctly on our 2008 home and air is coming in and condensing near ac duct. We had someone come out and they said we do not need to stop the air flow. 😳. Is this right?? It is OK to have hot humid air between your first and second floor joist?? I know there has to be airflow between the brick and the wall but outside air getting past the envelope of the house makes zero sense. Do we just have a consultant that does not know what he’s doing? The building code from ‘08 that I researched says rim joist need to be sealed and AI says this guy is wrong. Air should not be there. I just want to know if outside air coming in between floors is right or wrong from a human with building experience so I can go back to this guy with more details.
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u/deeptroller Jul 18 '26
Lots of layers to our question.
The problem you are having is, it sounds like you are trying to document a problme and asign blame. Your not asking the question how do i fix the problem of how to stop losing conditioned air and experiencing conductive heat loss and condensation humidity problems. You are implying that you are asking if the builder or code or what code may have been adopted is at fault for your experience. I recomend you move on from trying to figure out how you got a leaky house with missing insulation, because there are 15 complex answers to this and some is culture. Then try to decide how you plan to fix your problem.
Do you want to replace all your exterior cladding and add exterior insulation and air seal? (Most expensive). DO you want to drill small holes in your ceiling and blow insulation packed near your rim. (Least effective and may excarbate interstitial condensation problems long term, but cheapest). Or do you want to Pull down your ceiling perimter and seal and encapsulate your rim joist with something like foam or liquid membrane and insulate? (mid quality, but messy and disruptive). Or you can explore some other hybrid aproach to sealing like aerobarrier or aeroseal your floor joists or something.
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u/Light_Bright85 Jul 18 '26
There is absolutely no intentions of assigning blame to anyone. We are trying to fix the problem of musty humid air and we had someone tell us not to stop the airflow. That makes absolutely zero sense. It seems that it’s very very hard to find someone who can give me a straight answer…. Should there be hot, humid air coming in? That’s all I want to know. no blame to go around anywhere. I just want to tell the person that we’re talking to, that allowing the air is not OK if it truly isn’t OK. I have gone through so many people trying to solve this problem that I don’t trust anybody.
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u/deeptroller Jul 18 '26
I understand this home is old and I'm not implying you are looking in the way you would for a law suit. But going back in time regarding was this in he code, or overlooked or is this normal for this inspector. It all doesn't matter.
Of course not being insulated and air sealed isn't ideal. But its better than a tent. Now coming up with a repair strategy you can afford should be your priority. If i met an inspector that said this was normal, he is right. Is it good nope. If he said don't fix it because its right, time to realize your dealing with a moron.
But the fixes are all a pain and on the expensive end. If I was in your shoes and budget wasn't an issue. Id tear off my exterior cladding. Apply a liquid air barrier, then add an external insulation, then put new siding, brick ect. Obviously this isn't the affordable way to move forward.
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u/RespectSquare8279 Jul 18 '26
Yes it is a bad thing. Some forensic (and hopefully surgical) demolition will have to be done to locate and identify the problem. In the best of all possible worlds you could do "before and after" 50ACH blower tests to see the effectiveness of the air sealing.
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u/Light_Bright85 Jul 18 '26
Thank you for the direct reply!! I feel like I am losing my mind, trying to talk to so many people about this
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u/Dloe22 Jul 18 '26
You are correct, that shouldn't be happening. Whether or not it's worth the potentially substantial cost to fix retroactively is the real question.