How to handle melting frost in attic?


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Old 01-06-18, 01:54 PM
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How to handle melting frost in attic?

My entire attic is covered in frost. Not an exaggeration. I'm 99% positive it is due to one of my bath fans being routed to the attic and spreading all the hot shower air through out the attic.

I'll be getting a new roof this spring and will address that issue at that time.

My #1 priority right now is how to handle the frost once is melts. I just moved in last Summer and this is my first Winter in this house.

It's been single digits and dipping into the minus' for 2-3 weeks but now on Monday it will be 36F and im expecting this to melt all over the insulation. Only thing thats has came to mind was to great some kind of tarp layout and pitch it to one side and eventually try to vac out the water.

I hoping someone has a better method/idea!

https://www.youtube.com/watch?v=Q-2A...ature=youtu.be
 
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Old 01-06-18, 02:02 PM
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Frost often sublimates (evaporates from a solid into a gas) if you don't have a sudden spate of warm weather. There is also not a lot of liquid water if you simply have frost crystals. It is often absorbed by the plywood like a sponge and doesn't drip much, if any... but it depends how much frost you have... how much snow is on the roof, how quickly it warms up, whether the roof is in direct sun, etc.

Keep in mind your house has probably done this from the beginning of time, so this is nothing new. If you haven't had a leak before, you probably won't now either. While crawling in attics, I often see a few drips here or there in the insulation where you can see evidence of minor frost melt. It's rarely enough to cause a problem because the insulation sucks it up small quantities of water like a dry sponge.

On the other side of the coin, we can't see how much frost you are talking about. If it's an inch of ice, that's different. And repeated wetting of the roof sheathing and rafters can cause mold. So I would just monitor it... unless you provide more info that indicates a real problem. Wintertime frost is present in almost any home in North America where it gets below 0. And yes, fix any known ventilation problems that are making the frost worse.
 
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Old 01-06-18, 02:14 PM
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Click the youtube link at the bottom of the original post. It will show you how much frost.
 
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Old 01-06-18, 02:25 PM
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Yeah, that's a lot of frost. But how old is this house? It's likely nothing new... has happened every year since who knows when. Deal with it in the spring when you get a new roof. Put a tarp down and you will catch all the water but then where will it go? You will have concentrated it into a few smaller areas where it definitely will be a problem then.

I would still say let it be. Not ideal, but your insulation will be able to absorb whatever dripping takes place... after all, it has done it every year for who knows how long.
 
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Old 01-07-18, 07:09 AM
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I'd highly doubt all that frost was caused from that one fan.
Far more likely to be things like lack of air sealing, not enough insulation, lack of proper roof venting, soffit vents blocked with insulation.
In the spring I'd be up there looking for signs of mold or fungus and have it treated if there is.
Any exterminator can come in and do it with a product like this or it could be done DIY.
BORA-CARE® WITH MOLD-CARE® » Nisus Corp
 
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Old 01-07-18, 08:06 AM
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The issue is in 2 parts.

1. The bath fan vented to attic

2. Proper ventilation throughout the attic. The home inspector at the time mentioned that the roof didnt have certain end caps on the peak of the roof or something and its not ventilating as it should.

I do agree that this had to be happening for a long time I just hope this time around it doesn't cause an absolute **** storm.
 
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Old 01-15-18, 03:59 PM
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Guyfawkes,
What did you end up doing? I have frost in my attic as well, but only about 25% of what you had. It went from -20 to 60 degrees recently and I think it all melted in 24 hours and caused a few wet spots to show up in my sheet rocked ceiling.
I understand what causes frost and will tackle that next summer. In the interim, I am curious if you found a way to manage existing frost of it anyone has any suggestions.
I hope that with more stable temps that only minor frost forms and it sublimates come spring. I am just being overly cautious at this point.

Thanks!
 
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Old 01-15-18, 05:44 PM
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Look and fix any air leaks into the attic, hatch, exhaust fans, recessed lights, and such. Make sure the soffit venting is not blocked by insulation and that there are upper vents of some sort. If you are using a humidifier in the house turn it down or off.

Bud
 
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Old 01-16-18, 03:25 AM
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A few large fans blowing towards the frost would likely cause it to disappear..
 
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Old 01-16-18, 03:48 AM
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Have you re-directed the bathroom vent fan to the exterior ?

As a Broker, I've seen many homes where this condition is due to the vent duct just falling off the through-the-roof-vent; but yours sounds like it was originally designed to vent right into the attic; which has to be corrected.

If the duct didn't just fall off, I'd ask the Roofer you're going to use in the Spring how he'd be venting the bath fan, and implement that solution NOW.
 
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Old 01-16-18, 06:40 AM
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Thanks all.

My bathroom fan is indeed vented only to the attic. I knew this and we haven't run the fan in over a year. But it was still a hole and steamy showers were still passively venting up. I will work on an exterior vent this spring.

Until then I have done exactly as everyone has suggested:
-Sealed as many leaks as possible (air tight attic access and plugged bathroom vent)
-Stopped running a humidifier
-Placed a box fan in the attic to encourage airflow and sublimation
-I will monitor weekly and cross my fingers

I am not sure how to effectively seal electrical boxes in the ceiling. There are 8-10 when you count lights and smoke detectors and I am sure they all leak. Any tricks to that?

I have a dehumidifier, but it is only 24 degrees currently in the attic so it would likely freeze. When the temps rise, should I consider using a dehumidifier up there? I don't know anything about humidity or relative humidity. Is there a certain humidity I should be concerned with? It is currently 15%.
 
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Old 01-16-18, 07:10 AM
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If your attic is reasonably well vented then the dehumidifier would be dealing mostly with outside air and in the winter it has very little moisture.

To help understand Relative Humidity (RH) here is a link to a calculator I like. Since RH and temp are inversely related, RH goes up when the temp goes down, with no change in the quantity of moisture in the air. So comparing RH readings is difficult. I normalize all RH readings to one common temperature, I use 70°. Take any temp and RH reading and use the calculator to determine the dew point (DP). Use that DP and 70° to calculate what the RH would be if that air were warmed up to room temperature. Adjusting to one temp will tell you which area has the most moisture.

Since can foam does not expand well in very cold temperatures you can fabricate any type of enclosure over those electrical boxes. Drywall and caulking would be fireproof if that is a concern.

For the unused bath fan that may be passively leaking air into the attic, cover it with some plastic.

If you have a basement where you can access the ceiling joists and floor above seal everywhere you can. Check around plumbing, sinks, showers, and vent pipes. Any moisture in the basement will usually end up in the attic, and dirt floor crawlspaces are terrible.

Going too long so I'll stop for now.

Bud
 
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Old 01-16-18, 07:13 AM
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With the Bathroom Vent closed off . . . . your hot shower is still going to put a huge amount of water vapor into the atmosphere of your living quarters anyway . . . . maybe you can temporarily encourage the occupants to shower with the door open so that at least, this humidity is distributed throughout the dwelling and not concentrated in the bathroom walls.

I would talk to the Roofer and see if he can do now what he would do in the Spring anyway . . . . as far as the proper roof venting is concerned.

PS: I've also had people venting their stack pipes directly into the attic . . . . and then they get brown icicles hanging from the rafters !
 

Last edited by Vermont; 01-16-18 at 07:39 AM. Reason: Added PostScript
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Old 01-16-18, 07:28 AM
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Bit late but, use a shop vac with an extension hose and vacuum up the ice BEFORE it melts.
 
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Old 01-16-18, 08:06 AM
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Thanks guys, all very valuable advice. I will post an update with any new info.
 
 

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