Ceiling Condensation - HVAC Advice Needed

[looney2ns]

Take pictures when you do it! I'd like to do one but have no idea where I'd direct the air.

Out the roof with the proper termination boots.
Such as: Shop Broan Metal Roof Vent Kit at Lowes.com



NEVER just blow it into the attic space or crawl space.

See how here:http://www.thisoldhouse.com/toh/video/0,,20783011,00.html

 

[churchmouse]

Either out the soffit or out the roof with the proper termination boots.
Such as: Shop Broan Metal Roof Vent Kit at Lowes.com

or

Shop IMPERIAL Soffit Vents at Lowes.com
NEVER just blow it into the attic space or crawl space.

Exactly.......way to much humidity.

 

[woowoo2]

Ok, can do. I might vent it through the outside soffit. Not sure I'm comfortable cutting a hole in my roof quite yet.

Soffit Intake/Exhaust vent

This is the type of vent I used, gets the wet air away from the home.

 

[looney2ns]

No humidifier.

Anybody else want to weigh in on floor vs ceiling return vent? Should I add another one at the ceiling level?

Also considering the house fan. If I can't devise a very well sealed device to close it off, I think I'm removing it. I think I can though.

How much attic insulation do you have? Is it still in place as it should be? Not mashed down or moved by past work done in the attic?

 

[steveh_131]

How much attic insulation do you have? Is it still in place as it should be? Not mashed down or moved by past work done in the attic?

I'd like more, but it's decent. I've got a big bare spot around the chimney were it was wet and nasty from a ice dam leak in the winter. I'm going to fill it back in with the pink stuff.

 

[danimal]

All the new homes being built around here the builders are exhausting the bathroom and kitchen type vents into soffit vents. The only roof penetrations are for the furnace and sewage stack. The soffit vents are pretty hard to screw up, just be safe on the extension ladder if you DIY it.

We love our whole house fan. During the winter I use one of the 3M window kits to cover the louvers below and I made a box out of the 1.5" R-7.5 Owens Corning rigid foam to cover the fan and motor that I then throw a piece of R-38 over top of it up in the attic (when I installed the louvers I sealed all around it with silicone so I know the only air leakage is through the louvers). I never feel any air moving down through ours during the summer time, doesn't mean there's not, but I'd just be shocked if you have that much cooler air in the attic making it's way down into the house.

Do you have a hydrometer to check the humidity level of the upstairs vs. the downstairs. The dehumidifier I have in my basement is set to 60% and has a readout on it and the weatherstation upstairs stays pretty spot on with the unit downstairs since we keep the blower on all the time.

 

[churchmouse]

All the new homes being built around here the builders are exhausting the bathroom and kitchen type vents into soffit vents. The only roof penetrations are for the furnace and sewage stack. The soffit vents are pretty hard to screw up, just be safe on the extension ladder if you DIY it.

We love our whole house fan. During the winter I use one of the 3M window kits to cover the louvers below and I made a box out of the 1.5" R-7.5 Owens Corning rigid foam to cover the fan and motor that I then throw a piece of R-38 over top of it up in the attic (when I installed the louvers I sealed all around it with silicone so I know the only air leakage is through the louvers). I never feel any air moving down through ours during the summer time, doesn't mean there's not, but I'd just be shocked if you have that much cooler air in the attic making it's way down into the house.

Do you have a hydrometer to check the humidity level of the upstairs vs. the downstairs. The dehumidifier I have in my basement is set to 60% and has a readout on it and the weatherstation upstairs stays pretty spot on with the unit downstairs since we keep the blower on all the time.

His dampers do not look sound in the pic.
Wet air and dry air are always looking to exchange. Dry air will suck the wet air in this attempt. Same with temp. differences. They are always attempting to balance.

 

[CHCRandy]

Man that is a lot of water. What type roof vents do you have? Do you have good soffit intake venting? Is insulation not blocking flow of air from soffits to roof vents? Does your house have vents in the gables?

I think you have a serious ventilation issue somewhere.

I had a guy back in the winter who had a similar issue....come to find out his humidifier on furnace was at about 45%, we moved it to 30-35% and it solved the problem. Don't ask me how or why it worked....I just did what my air flow expert out of Chicago advised....and it worked.

Good luck. That looks interesting.

 

[steveh_131]

Do you have a hydrometer to check the humidity level of the upstairs vs. the downstairs. The dehumidifier I have in my basement is set to 60% and has a readout on it and the weatherstation upstairs stays pretty spot on with the unit downstairs since we keep the blower on all the time.

Yes, I checked it upstairs during these condensation episodes and it's around 65-70% at counter-top height with the AC running. I should hold it up to the ceiling and check there.

My dehumidifier is downstairs, but I have the intake downstairs sealed up because it got so dang cold down there during the summer. Should I open that back up? I still have the vents sealed. My basement is connected to the upper level by open stairs.

His dampers do not look sound in the pic.

No, the whole house fan louvers are bent up and leaky. I can see huge gaps in them when they're supposed to be closed. Getting it sealed off is high on the priority list.

What type roof vents do you have? Do you have good soffit intake venting? Is insulation not blocking flow of air from soffits to roof vents? Does your house have vents in the gables?

It has soffit vents, but I haven't checked them for blockage yet. My attic is a nightmare to navigate because it's so short and I'm highly allergic to dust. Time to get on a mask and get my lazy butt up there again.

No gables, it's a ranch house. I have peak vents. It didn't seem terribly hot up there so I guessed that the airflow was ok, but then the ice dams might indicate otherwise.

Would attic airflow contribute to this? Seems like a really hot attic would make my ceilings hot and prevent the condensation.

 

[CHCRandy]

[/QUOTE]It has soffit vents, but I haven't checked them for blockage yet. My attic is a nightmare to navigate because it's so short and I'm highly allergic to dust. Time to get on a mask and get my lazy butt up there again.

No gables, it's a ranch house. I have peak vents. It didn't seem terribly hot up there so I guessed that the airflow was ok, but then the ice dams might indicate otherwise.

Would attic airflow contribute to this? Seems like a really hot attic would make my ceilings hot and prevent the condensation.[/QUOTE]

To be honest, the condensation is a little out of my expertise, but I can tell you that ventilation in the attic is essential. I have seen it completely ruin decking on a house....just rot it away. I think you need to first check and make sure insulation isnt blocking soffit vents, then check your ridge vents on the underside to make sure they are cut out. You would be surprised how many scabs will install a roof and not cut out vents....because they know the homeowner will never look, and other times they just forget to cut the black paper...vents may appear to be there from outside but when you go in attic, check them out to make sure plywood and black paper are cut back. You can at least eliminate this from being a problem pretty quickly.

I would think if your attic isnt venting but house is cool, if you have decent insulation it will hold cold air in house, attic would heat up.....somewhere the hot and cold has to meet, which could be above the drywall but below the insulation....and that could form condensation. But like I say...that is just me logically thinking.

I can tell you most ice dams are caused by this exact thing. If we can keep air moving...ice dams don't like to form, but if there is no/little insulation and no/little ventilation...the chances are good you will get ice dams. Good luck and hope you get it figured out. That looks like a pita.

 

[BigBoxaJunk]

When my house was built, I saw that they put plastic vapor barrier on exterior walls, but not on the ceiling. The builder said that if they put plastic on the ceiling in this climate, I'd get condensation.

One thing I'd try is to leave your AC fan on all the time for a week or two and see if that helps. I do that when it's either really hot or really cold.

 

[looney2ns]

When my house was built, I saw that they put plastic vapor barrier on exterior walls, but not on the ceiling. The builder said that if they put plastic on the ceiling in this climate, I'd get condensation.

BS. Not if the attic is properly insulated. And living space is properly vented with exhaust fans.
Builders get away with all sorts of stupid crap.

Op, you say that the humidity in the upper portion of the house is 70%!!!! Holy COW! That adds a lot of load on your A/C unit. If you don't have mold problems, I'll be surprised. It needs to be below 50%.

Soffits, if they are vented soffits, are the wrong place for vent fan exhaust, as pointed out in the This Old House video I posted. Contractors do it because it's easier, and less labor thus cheaper, not because it's the best way.

Ice Dams: Are caused more times then not by poor attic insulation. Heat escapes through the ceiling, and melts the snow from underneath, then at night it all refreezes. Next day, cycle continues, problem grows. Yes proper attic ventilation can help, but it's not the entire cause.

Higher return air vents: If your attic insulation is good, and if any ceiling penetrations to the attic were properly sealed, this becomes less important.

If your attic insulation isn't somewhere at R40 or higher, it's not adequate.

You really need to get the humidity level consistently below 50%.

 

[BigBoxaJunk]

You need a good vent fan in that bathroom....today. Installed, sized and vented properly, and used.

The Panasonic's are hard to beat.
https://www.acwholesalers.com/Panas...rz2CCHjLuESC72EmuAt0pBbJ9hixMMxl88aApBX8P8HAQ

The high-end bathroom vent fans brag about how quiet they are. Am I the only guy who appreciates the occasional usefulness of a nice loud bathroom fan?

 

[Rookie]

The high-end bathroom vent fans brag about how quiet they are. Am I the only guy who appreciates the occasional usefulness of a nice loud bathroom fan?

Lol, my wife insisted on getting a louder fan for the very reason you refer to. I keep having to explain that the fan doesn't work as she intended when she LEAVES THE DAMN DOOR OPEN!!!

 

[CHCRandy]

Ice Dams: Are caused more times then not by poor attic insulation. Heat escapes through the ceiling, and melts the snow from underneath, then at night it all refreezes. Next day, cycle continues, problem grows. Yes proper attic ventilation can help, but it's not the entire cause.

Nor is insulation......that is why I said both of them. You could have 10 feet of insulation but the sun can still heat the roof, causing melting and ice dams. You can never stop radiant heat completely. Roof ventilation is important for achieving a uniform roof decking temperature....if you can keep decking underside the same temperature everywhere.....you have a better chance of it melting to the gutter.

 

[jamil]

After we had our house built the inspector we hired used a thermal imager as part of his inspection. It allows you to visually see where temperatures differ. He found a few areas where insulation was sub par. It was in the winter and there was a dark blue spot where everything else around it was yellow. Had the insulation guy hem-hawing.

I think Home Depot rents thermal imagers pretty cheap. It may be worth it to rent one for a day and check your whole house for problem areas. You'll be able to see exactly how much impact the whole house fan has on hot days. Best to do it on a day where delta between inside and outside temps is fairly high to show up the hotspots.

 

[looney2ns]

Nor is insulation......that is why I said both of them. You could have 10 feet of insulation but the sun can still heat the roof, causing melting and ice dams. You can never stop radiant heat completely. Roof ventilation is important for achieving a uniform roof decking temperature....if you can keep decking underside the same temperature everywhere.....you have a better chance of it melting to the gutter.

I suspect the heat that is being lost in the winter through the fan shutters is his biggest contributing factor in the ice dam issue here.

 

[steveh_131]

Alright guys, project of the week is to seal up that house fan. The assembly protruding from the ceiling is all metal, and is quite warm to the touch. I can feel gigantic amounts of heat coming in when I hold my hand up to it.

Here's my idea: Build a thin wooden box lined with foam board to seal directly to the ceiling all around the box fan.

I have some of this around:

I thought I might use that to keep it as air-tight as possible around where it makes contact with the ceiling and the wall.

Any expert opinions on this design? I have 4 very strong speaker magnets that I thought I might use to hold it to the fan.

The R-value on this foam board isn't huge. How big of a deal is that?

Thanks, guys.

 

[jamil]

I think you need to be careful. The metal transfers the outside temperature into the inside. To prevent that you would need to insulate the metal from the inside air. Even if you build a box around it, if there's air inside the box, it would probably condense, especially in the winter, and may eventually mold. I think I would just remove the fan and seal up the hole, and insulate where it was.

 

[steveh_131]

I think you need to be careful. The metal transfers the outside temperature into the inside. To prevent that you would need to insulate the metal from the inside air. Even if you build a box around it, if there's air inside the box, it would probably condense, especially in the winter, and may eventually mold. I think I would just remove the fan and seal up the hole, and insulate where it was.

That's an interesting thought, but the house fan shutters don't seal at all when they close. There are literally 1/2" gaps along each one, allowing air to circulate quite freely.

Given the free air circulation with the attic, do you think this would still be an issue?