# Cool spots



## Windows on Wash (Aug 30, 2011)

Dormers are notorious leakers at the roof interface. If you have piled up snow, that is problematic.

What is the relative humidity level in the home?


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## Mingom (Feb 16, 2015)

Thanks for the quick reply. During the day it's low 30's % at night with the humidifier maybe in the 50's% range. I've attached a picture of where it's occurring.


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## Mingom (Feb 16, 2015)

Also, the spots are occurring in random spots, not where the interface is really.


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## jimn (Nov 13, 2010)

What is the outside temp? 50% humidity sounds way high for cold climates. Could be just condensation. Here is one guide . The recommended maximum is 40% and that is when outside temp is above freezing. 

http://www.homeenergyresourcemn.org...ectCatID=795&CatId=795&ref=795:HYHW_I_LEFTNAV


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## SeniorSitizen (Sep 10, 2012)

Check the temperature of the cool spots to determine if condensation is possible.


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## Windows on Wash (Aug 30, 2011)

Big +1. 

50% with the overnight lows is way, way, too low if it is cold where you are.


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## Mingom (Feb 16, 2015)

Thanks for the input everyone. I thought it might be due to just the humidity level, but I hadn't seen a chart like that before. I will try and hit it with an temp gun tomorrow to see what I'm getting for numbers. It's been a cold winter so it makes sense to see that if we've been running the humidifier.


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## SeniorSitizen (Sep 10, 2012)

I'm having doubts about condensation in that area. If the humidity measurement is anywhere close to being accurate, we can see that if we adjust - as an example - this link room temperature to 70°F with the RH at 40 % and solving for dew point temp. the surface temperature would need to be 44°F to form condensation. 

http://dpcalc.org/


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## Windows on Wash (Aug 30, 2011)

SeniorSitizen said:


> I'm having doubts about condensation in that area. If the humidity measurement is anywhere close to being accurate, we can see that if we adjust - as an example - this link room temperature to 70°F with the RH at 40 % and solving for dew point temp. the surface temperature would need to be 44°F to form condensation.
> 
> http://dpcalc.org/


I can bet you that in that dormer, that section is poorly insulated. 

They are always done poorly and if so, the surface temp is going to be way low.


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## Mingom (Feb 16, 2015)

The spots only occur in the early morning - that suggests to me that the issue could be condensation - if it was a leak wouldn't it appear later, when things are actually melting on the roof? 

I've reattached the picture again with circles of where we have seen the spots - one is pretty visible in the picture. I don't know if it has to do with the dormer as it is really on the regular part of the roof line and not the dormer portion.


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## HomeSealed (Jan 3, 2008)

The random spots would suggest missing insulation. You could call someone to come in with a thermal cam to confirm, otherwise you should be able to feel/see a temp difference in those areas. 
If that is the case, you may want to consider dense packing those slopes with cellulose.


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## Mingom (Feb 16, 2015)

I imagine you're correct- I haven't been able to check the temp yet - but not using the humidifier has helped. I'm thinking there is voids in the insulation or long nails in those spots.


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