metal cold roof question ..... - Contractor Talk - Professional Construction and Remodeling Forum

Vermonster · 07-13-2007, 06:53 AM

On one of my remodel job the client just had to have a metal roof and hired his own metal roof contractor.

I only do shingle roofs, no metal. Here is my question for you metal roof installers. When I install a cold roof I create a real open air space atop of the decking, underneath the shingles. No insulation in that space as it would negate the whole cold roof concept as it is my understanding.

This metal roofing contractor is running 2x4 sleepers over the existing shingle roof, then he installs rigid insulation in the space between the 2x4s (I assumefor rigidity of the flimsy metal panels he uses).

With insulation in the space between the metal and the "decking", is this still considered a cold roof?

Thanks ........

**joasis** · 07-13-2007, 07:44 AM

The term "cold roof" isn't something I am familiar with, being in Oklahoma, but the practice you are describing is acceptable. You stated the roof panels are "flimsy"?

I guess I need to get up to speed on cold roofing from the northerners, but it sounds like you really don't like metal roofing.

K2 · 07-13-2007, 07:46 AM

I haven't heard that term in quite a few years but I haven't worked in the mountains in a while either.

copied:

Quote:

Cold Roof Ventilation & Ice Damming
In central Colorado and other mountainous regions, ice damming is an epidemic problem that results in not only damage to the interior and exterior of structures, but is a safety issue that can be life-threatening for pedestrian and vehicular traffic. To effectively combat ice damming, multiple design and construction factors must be considered and implemented to prevent this phenomenon from occurring.
Ice damming is the result of snow or ice that melts at upper roof sections and re-freezes when it flows to the cold eave sections. While there are several different approaches to reducing or eliminating ice
InfraMation 2003 ITC 092 A 2003-08-15
damming altogether, the approach that has proven to be the most effective through our studies has been the cold roof design. A cold roof is designed to provide a uniform and consistent cross-flow ventilation path from the eave to the ridge of a roof resulting in a more uniform temperature equilibrium across the roof’s sheathed surface. By maintaining a roof temperature of the closer to equilibrium to the outside ambient air temperature, ice damming is significantly reduced because the eave surfaces are now in equilibrium with the up slope roof surfaces (no hot spots). Another roof design concept for mountainous regions to control ice damming is that of the super-insulated roofing system. In theory such a system will work effectively; however the incorporation of 100% vapor barriers at the ceiling level, control of ceiling penetrations such as chimneys, and recessed can lights must be eliminated or designed and detailed properly in order for the system to achieve the desired performance. Solar gain must be considered in both designs, as it may circumvent any roof system.

K2 · 07-13-2007, 02:51 PM

In the mountain areas I worked way back, cold roofs were not required on 12/12's or steeper.

Vermonster · 07-13-2007, 03:53 PM

Quote:

Originally Posted by joasis

The term "cold roof" isn't something I am familiar with, being in Oklahoma, but the practice you are describing is acceptable. You stated the roof panels are "flimsy"?

I guess I need to get up to speed on cold roofing from the northerners, but it sounds like you really don't like metal roofing.

I don't mind metal roofs at all .... it's just that I don't do them. My main issue is that it was sold as a cold roof, when in fact - at least in my opinion - the insulation makes it a regular roof construction. Or am I wrong here?

By the way ... in the European Alps cold roofs are making a huge comeback. Rake boards of over 2 feet are not uncommon.

**joasis** · 07-13-2007, 06:10 PM

If the metal panels are on EPS insulation, I would venture to say they will not pick up any heat from the attic, and be as cold as the outside temps...so I guess it would qualify as a cold roof. One of the benifits of Oklahoma is never having to deal with those issues. However, I noticed last week traveling through New Mexico, most of the new construction is going metal.

jmorgan · 07-14-2007, 06:39 PM

Check and see if he is leaving an air gap between the insulation and his matal panels. We do similar systems, but are carefull to leave an 1" or better air space. Sometimes have had to use 2x6 sleepers.
Jim

theroofinggod · 07-15-2007, 11:10 PM

if the air space is above awell insulated heated area where no heat escapes to the bottom of the decking ,it`s technically a cold roof application,where there air temp above and below the roofsheathing are similar and don`t attract condensation as the dew point is at the lower insulated ceiling area

K2 · 07-15-2007, 11:21 PM

I think the the op is talking about roof sheathing then sleepers then roof sheathing again then shingles to create a cold roof. That is how I did it and how I believe it is still done in the Colorado high country.

Vermonster · 07-16-2007, 07:45 AM

Quote:

Originally Posted by K2eoj

I think the the op is talking about roof sheathing then sleepers then roof sheathing again then shingles to create a cold roof. That is how I did it and how I believe it is still done in the Colorado high country.

That's exactly what I am talking about. That is what I construct when I build a cold roof. To me there has to be a completely open, ventilated airspace between the attic decking and the shingle decking of at least 3" or so. Anything less just wouldn't do - in my opinion.

With a metal roof who really cares. There just won't be any ice damming or leaks anyway. I am just talking about the principle of selling a cold roof when it is not.

Thanks .........

K2 · 07-16-2007, 08:04 AM

Quote:

Originally Posted by Vermonster

That's exactly what I am talking about. That is what I construct when I build a cold roof. To me there has to be a completely open, ventilated airspace between the attic decking and the shingle decking of at least 3" or so. Anything less just wouldn't do - in my opinion.

With a metal roof who really cares. There just won't be any ice damming or leaks anyway. I am just talking about the principle of selling a cold roof when it is not.

Thanks .........

I've seen ice damming on low pitched metal roofs. I've also seen major hail storms cause ponding and serious leaking on metal. Of course hail is a different animal and freeze/ thaw is not the issue .

tnt specialty · 07-16-2007, 09:28 PM

Your right, it's not a cold roof.

roofwiz74 · 07-17-2007, 01:47 AM

ya'll are killing me.

Vermonster · 07-17-2007, 06:50 AM

Quote:

Originally Posted by roofwiz74

ya'll are killing me.

.... and why is that?

roofwiz74 · 07-17-2007, 10:03 PM

if you don't know,don't post.
for the time it takes to post what you think is....you could google and find out.

roofwiz74 · 07-17-2007, 10:04 PM

or ask me

K2 · 07-17-2007, 10:35 PM

Quote:

Originally Posted by roofwiz74

or ask me

Tell us.. Type away.

roofwiz74 · 07-18-2007, 12:31 AM

actually I'm full of it and had to google it myself,just wanted some excitement.

Vermonster · 07-19-2007, 06:29 AM

I know how to build a conventional cold roof. My question was specific to metal roof, which is something I don't do.
Thanks .......

K2 · 07-19-2007, 08:04 AM

Quote:

Originally Posted by Vermonster

I know how to build a conventional cold roof. My question was specific to metal roof, which is something I don't do.
Thanks .......

I don't think you will find a "national standard" on Cold Roofs. Your local building dept should have the only answer that really matters.