Roof & Insulation Specialist needed


#1

I’m looking for someone to give me their expert advice. I have a stone cottage in Presque Isle Michigan and have recently done a restore and added a second story over half of it. The new second story roof has extreme icedamming. The roof is rafters 2x12’s (cathedral) with R38c insulation (10 1/4") the builder did NOT use baffles and there is a ridge vent with soffit vents. The interior walls are T&G cedar. I need to get a professional willing to come out and give me advise on what is wrong and how to fix the problem so that I can bring the facts to the builder who seems to think that it’s just the weather we have had this year and oh by the way “I did forget to vent the area of the roof that butts up against the faux chimney”. I’m not real eager to have him start making his fixes until I get someone up there that can give me their unbaised advice. I haven’t had any luck on finding someone through the yellow pages in the Presque Isle area any help would be greatly appreciated. Thank you in advance, Sandra


#2

I would have to see exactly whats going on before i can make any determination on anything. I can try to help,if you would like.

If the are no baffles in the ceiling and r38 up there with ridge vent you might have problems. If the drywall is up then it becomes a real problem. Is there soffit vents at the eaves??


#3

We do not have drywall but used Tongue and Groove Cedar. And yes there are soffit vents that run along each side of the house. The last time we were up I noticed icicles coming out of the vent in one area, I did take pictures.


#4

Ice Damming means heat loss through the ceiling. So R38 is not enough.

Ventilation is supposed to dissipate the residual heat leaking through the insulation. For ventilation to work, you need an intake (usually at the soffits), a clear air channel of at least 4 inches height, and an exhaust at the high point of the roof. The need for having about 4 inches clear for the air channel is that air has viscosity (resistance to flow), and the narrower the channel, the more difficult it is for air to move by convection. 4 inches is about the minimum to provide a large enough opening for the viscosity of air not to reduce the flow rate. From your description, it does not appear you have enough clear air space to allow good air movement.

The openings for air intake and exhaust should be based on the 1:150 rule (although the minimum is 1:300), where there is one sq.ft. of ventilation for every 150 sq. ft. of attic space. This should be split 50/50 between intake and exhaust.

Reading your description, it appears that the existing insulation lets enough heat through to warm the air between it and the sheathing. With the residual air channel being less than four inches, the heated air transfers its energy to the deck above, before it can be moved out by convection. With snow being an excellent insulator, the heat is trapped until the decking reaches the freezing point, and the snow on top starts to melt. Then it runs down until it reaches a space with no more heat, and freezes, making the ice dam.

Do you have a vapour barrier behind the T&G cedar? If not, you could also have moisture migration from the living space into the insulated “cold” space, where it can condense.


#5

Ice Damming means heat loss through the ceiling. So R38 is not enough.

Ventilation is supposed to dissipate the residual heat leaking through the insulation. For ventilation to work, you need an intake (usually at the soffits), a clear air channel of at least 4 inches height, and an exhaust at the high point of the roof. The need for having about 4 inches clear for the air channel is that air has viscosity (resistance to flow), and the narrower the channel, the more difficult it is for air to move by convection. 4 inches is about the minimum to provide a large enough opening for the viscosity of air not to reduce the flow rate. From your description, it does not appear you have enough clear air space to allow good air movement.

The openings for air intake and exhaust should be based on the 1:150 rule (although the minimum is 1:300), where there is one sq.ft. of ventilation for every 150 sq. ft. of attic space. This should be split 50/50 between intake and exhaust.

Reading your description, it appears that the existing insulation lets enough heat through to warm the air between it and the sheathing. With the residual air channel being less than four inches, the heated air transfers its energy to the deck above, before it can be moved out by convection. With snow being an excellent insulator, the heat is trapped until the decking reaches the freezing point, and the snow on top starts to melt. Then it runs down until it reaches a space with no more heat, and freezes, making the ice dam.

Do you have a vapour barrier behind the T&G cedar? If not, you could also have moisture migration from the living space into the insulated “cold” space, where it can condense.


#6

You can either email me the pics or post them here. Im not sure how to post them others know this here.

Let me get this straight, you have T/G up arready with no baffles correct?

This is a vaction home im assuming?

I would need the ammount of soffit vents or is it continious?

Is the area with the insulation packed with zero room for air?

From owens corning the ammount of insulation is at the minimum. If there is ice at the eaves yes there is some heat loss. On a cathedral ceiling you can only have so much insulation then your out of room.

Like i said send me a pic so i can see what you are talking about.


#7

To post a picture, I suggest you start by opening a Photobucket account (for free). You need a “host site”… once you upload pictures to Photobucket, single click the “IMG Code” space below the photo.

Then, without doing any additional “copying” functions, click in the text box of your posting.

R click & use the “Paste” option (or on your keyboard, press the control “ctrl” key & the letter “V” @ the same time. This is called ctrl+v) It should paste the link from Photobucket.

Continue your message & the picture should show up in the message.


#8

Yes there is T&G on the ceililng with R-38c with paper to the inside there are 2x12 rafters with no baffles that gives us 1 inch of clearance for airspace. The soffit vents are continuous and there is a ridge vent.
This is a vacation home at the moment but the builder was aware that we intend on moving up north in the next couple of years and we stated to him that we wanted to have an efficient home because of rising costs. Here are a few of the pictures: http://i158.photobucket.com/albums/t117/SandraBee123/rightside3.jpg http://i158.photobucket.com/albums/t117/SandraBee123/rightside.jpg http://i158.photobucket.com/albums/t117/SandraBee123/leftsideview.jpg http://i158.photobucket.com/albums/t117/SandraBee123/leftside2ndstorysoffiticicles.jpg http://i158.photobucket.com/albums/t117/SandraBee123/closeupsoffiticicles.jpg I hope this works Thanks RanchHandRoofing for the great directions.


#9

You’re

welcome… :mrgreen: