Public Service Announcement: Evaporation and Mold

[otrips]

You mentioned your attic has vents at the tops. it also needs soffit vents. The vents on the top will allow the hot air to escape but only if there are vents in the eaves to allow the colder air in. Think of your attic like a giant chimney and the eves as a damper. If you completely close the damper your going to have issues. Also think what would happen if you blocked the return vents for you furnace.
Attics need ventilation, otherwise the entire roof will heat up the lifespan of the shingles will be severely reduced and your way more likely to get ice damns in winter which will destroy you roof and possibly your whole house from water damage. They are required by code in most areas. Without lower vents your attic still needs to breath and will try and suck more air (humid air) out of the living space though even the smallest of openings, up the walls, etc...

 

[sneeyatch]

Many years ago, I knew a guy who had a large tank (180 plus). That was set up fairly close to the AC intake return. The evaporation caused his AC system to rust out.

 

[sleepydoc]

I can't say for sure, but I suspect this is caused as much by improper insulation/vapor barrier in your ceiling and/or improper venting of your attic. I'd also check to make sure there are no vents venting into the attic instead of outside.

Our former house was built in '56 and the previous owner had installed a bathroom fan that vented directly into the attic instead of outside. We were in the house 3-4 years before I discovered it, and I'm sure it was there several years before we moved in. Even with the humid air from the bathroom being vented out on a daily basis in a climate where temperatures go as low as -30ºF, there were no problems with ice or mold under the roof.

@sneeyatch: if the tank was right next to the AC intake it was most likely the salt rather than the humidity that caused the problems.

@wildman: I completely agree with the other posters; sealing the top with a glass top creates problems with gas exchange and heat buildup, as well as interfering with light transmission.

 

[SoloGarth]

You mentioned your attic has vents at the tops. it also needs soffit vents. The vents on the top will allow the hot air to escape but only if there are vents in the eaves to allow the colder air in. Think of your attic like a giant chimney and the eves as a damper. If you completely close the damper your going to have issues. Also think what would happen if you blocked the return vents for you furnace.
Attics need ventilation, otherwise the entire roof will heat up the lifespan of the shingles will be severely reduced and your way more likely to get ice damns in winter which will destroy you roof and possibly your whole house from water damage. They are required by code in most areas. Without lower vents your attic still needs to breath and will try and suck more air (humid air) out of the living space though even the smallest of openings, up the walls, etc...

Yeah agreed. This is the problem with how my house was built. The soffit vents (I believe that's what that foam thing is) are there but they packed 9.5" of insulation into a 9" space. So bad job on that guys. Haha. Just had no reason to look until now and I suspect this is probably done often by shoddy contractors. They certainly screwed me.

 

[SoloGarth]

I can't say for sure, but I suspect this is caused as much by improper insulation/vapor barrier in your ceiling and/or improper venting of your attic. I'd also check to make sure there are no vents venting into the attic instead of outside.

Our former house was built in '56 and the previous owner had installed a bathroom fan that vented directly into the attic instead of outside. We were in the house 3-4 years before I discovered it, and I'm sure it was there several years before we moved in. Even with the humid air from the bathroom being vented out on a daily basis in a climate where temperatures go as low as -30ºF, there were no problems with ice or mold under the roof.

@sneeyatch: if the tank was right next to the AC intake it was most likely the salt rather than the humidity that caused the problems.

@wildman: I completely agree with the other posters; sealing the top with a glass top creates problems with gas exchange and heat buildup, as well as interfering with light transmission.

Yes I agree. My concern though is that other people's house might have similar construction mistakes. These problems might not be a big deal for "normal" people. But reefers are a different breed haha. Anyway I wanted to bring it up in hopes that people will take a look. If I'm the only one that's awesome. I just had no idea it was happening for years and now it's too late for simple fixes.

 

[sleepydoc]

Yes I agree. My concern though is that other people's house might have similar construction mistakes. These problems might not be a big deal for "normal" people. But reefers are a different breed haha. Anyway I wanted to bring it up in hopes that people will take a look. If I'm the only one that's awesome. I just had no idea it was happening for years and now it's too late for simple fixes.

Yeah, unfortunately construction 'mistakes' are all too common. Good luck getting your problem fixed.

 

[SoloGarth]

Public Service Announcement: Evaporation and Mold

Yeah, unfortunately construction 'mistakes' are all too common. Good luck getting your problem fixed.

Thanks. My father is a contractor. Probably mentioned that earlier haha. But his work is the best. The plan is to remove the shingles plywood and insulation. Then reinsulate with closed cell foam 7" or 8" thick. This creates a proper vapor barrier, a proper vent area and increases my roof's insulation from R30 (although since this is compressed I'm sure it is significantly less) to R42 - R48. It gets cold here and anything reducing my heat bills is welcome.

 

[sleepydoc]

Thanks. My father is a contractor. Probably mentioned that earlier haha. But his work is the best. The plan is to remove the shingles plywood and insulation. Then reinsulate with closed cell foam 7" or 8" thick. This creates a proper vapor barrier, a proper vent area and increases my roof's insulation from R30 (although since this is compressed I'm sure it is significantly less) to R42 - R48. It gets cold here and anything reducing my heat bills is welcome.

Closed cell foam is expensive, but it really good at stuff like this. Like you said, it creates a vapor barrier and insulates without any gaps. Just having the ceiling/attic interface sealed will probably make a big difference in your heating bill. If you were getting that much moisture in the attic from the living space you probably had a ton of air leakage.

I have a new house and the builder didn't properly seal the spaces between my son's room and the garage (his room is over the garage.) I ended up hiring a contractor to take out the existing blown fiberglass and blow the area under his floor with closed cell. Made a big difference.

 

[SoloGarth]

Closed cell foam is expensive, but it really good at stuff like this. Like you said, it creates a vapor barrier and insulates without any gaps. Just having the ceiling/attic interface sealed will probably make a big difference in your heating bill. If you were getting that much moisture in the attic from the living space you probably had a ton of air leakage.



I have a new house and the builder didn't properly seal the spaces between my son's room and the garage (his room is over the garage.) I ended up hiring a contractor to take out the existing blown fiberglass and blow the area under his floor with closed cell. Made a big difference.

Glad to hear that. Yeah I told my dad that if we are taking the roof off might as well use the best insulation. Haha. I have no doubt that this project is going to be very expensive.

Yes I do think I had significant air leakage. Or something. One thing that is counter intuitive is that installing and running a powerful dehumidifier makes the house feel warmer and *seems to result in less runtime on the furnace. Difficult to tell as the weather is swinging around crazily this year. Anyway in some way I was losing a lot of heat to the roof.

 

[m1k3]

Pardon if already mentioned but don't have time to read the whole thread. I suspect you attic space, as small as it is, is not adequately ventilated. Since you will be redoing your roof anyway look into adding active attic vent fans or at a minimum a ridge vent. And make sure your soffit vents are not covered with insulation.

 

[SoloGarth]

Pardon if already mentioned but don't have time to read the whole thread. I suspect you attic space, as small as it is, is not adequately ventilated. Since you will be redoing your roof anyway look into adding active attic vent fans or at a minimum a ridge vent. And make sure your soffit vents are not covered with insulation.

Yup already discussed.

 

[wildman926]

@wildman: I completely agree with the other posters; sealing the top with a glass top creates problems with gas exchange and heat buildup, as well as interfering with light transmission.

The top is not totally sealed, so gas exchange still occurs. Heat buildup? None.... Open sump, and open back stand fixes that issue. Light transmission is reduced by only 5-12% max. With LED's, I just increase the intensity. From experience, I don't have these issues. Plan accordingly....

 

[SoloGarth]

The top is not totally sealed, so gas exchange still occurs. Heat buildup? None.... Open sump, and open back stand fixes that issue. Light transmission is reduced by only 5-12% max. With LED's, I just increase the intensity. From experience, I don't have these issues. Plan accordingly....

Well let's not turn this into a glass top vs no top debate please. To each his own. It's also been debated to death elsewhere. No one is gong to switch camps based on this thread haha.

 

[mike810]

If I may ask, how big is your house? I can see evaporation being a problem in a smaller house.

 

[mgraf]

Add vents, gable, ridge, roof top, whatever. I don't know how old your house is but, with better insulations and house wraps, mold has become a bigger issue in recent years. Houses are built "tighter" these days. Less areas for moisture to escape. I'm not saying at this point, you shouldn't replace your roof but, once they do, make sure you have good ventilation for your attic space.

 

[SoloGarth]

If I may ask, how big is your house? I can see evaporation being a problem in a smaller house.

It's medium- large. 1750 sq feet. But due to this 15' ceilings if it had another floor it would be close to double that.

 

[SoloGarth]

Add vents, gable, ridge, roof top, whatever. I don't know how old your house is but, with better insulations and house wraps, mold has become a bigger issue in recent years. Houses are built "tighter" these days. Less areas for moisture to escape. I'm not saying at this point, you shouldn't replace your roof but, once they do, make sure you have good ventilation for your attic space.

It was built in 92. And yes that's the plan.

 

[jfuka78]

Sounds like a venting issue, I had similar issue happen to me this year. I had my roof replaced a year ago and added a ridge vent and kept my slant backs on also. This winter I went in my attic and noticed mold on trusses and plywood. Plywood was wet also. I called the contractor and he informed me that the ridge needs to be taken off because the air is flowing between the ridge and slants and not the eaves and the ridge properly. Had to have dried out, cleaned, and sprayed with that white stuff
I have a 180 in my basement and evaporate about 2 gallons a day also if not more. My floor joist show no mold above tank.

 

[SoloGarth]

Sounds like a venting issue, I had similar issue happen to me this year. I had my roof replaced a year ago and added a ridge vent and kept my slant backs on also. This winter I went in my attic and noticed mold on trusses and plywood. Plywood was wet also. I called the contractor and he informed me that the ridge needs to be taken off because the air is flowing between the ridge and slants and not the eaves and the ridge properly. Had to have dried out, cleaned, and sprayed with that white stuff
I have a 180 in my basement and evaporate about 2 gallons a day also if not more. My floor joist show no mold above tank.

Yeah the moisture only seems to condense on cold surfaces. Which makes sense. But it also means you won't see that it's happening unless you are up there looking.