Guest User
2/2/2006
I have a very old shake roof over 2x6 tongue and groove redwood that needs to be replaces (an Eichler Atrium model if that means anything to anyone). Because of some other work that I am going to have done, I will have the original shake taken off and have the bare 2x6's open to the sky. We want to add insulation, and I have spoken to three different roofers with metal roof experience and had three different suggestions - none of which sound completely right. BTW, they all suggested Metro Shake roofing to match the look and feel of the neighborhood. Roofer #1 said to put down polyiso foam board and then plywood (I would prefer a bonded foam/plywood solution, but that's a detail). Then put down horizontal battens with a foam wedge under the shakes so the roof would be walkable. Roofer #2 wants to do the same as #1, but not put down the wedges. Roofer #3 wanted to put down 2x2's as vertical battens, add rolled fibreglass between the battens and then put horizontal battens and nail the metal shake panels to the edge of the battens. There would be no underlayment directly under the tiles so it wouldn't be very walkable (or you would have to walk very precisely on the edges to get the horizontal battens. The problem with #1 and #2 are that they both said that there is no need to ventilate under the shingles. #3 said that there was a need to ventilate, but he didn't see a need to put down a decking (which makes me concerned about walkability and warping) and #3 also said that shingles applied directly to a decking use vertical nails which tend to leak (which makes sense to me). From reading this I understand that I need to ask all of them to put down a vapor barrier, but the discussion here on ventilation under metal roofs has me concerned about #1 and #2. Do any of these sound flawed? What questions should I ask them? What is the name of a "wedge" insulation that could go under the Metro Shake II shingles and provide some level of rigidity. Thanks,
Allan Reid
Dura-Loc Roofing Systems, Inc.
2/3/2006
First you do not state whether it is a vaulted ceiling or attic type roof assembly. Adding insulation at the roof level on an attic assembly is of limited benefit. Most important is to ensure adequate ventilation and to have an air space under the roof covering. In vaulted assemblies the code calls for 1" minimum of vented free air and in attic situations you need to provide 1 sf of venting for every 150 sf of ceiling area minimum and 50% at ridge/eave. Next is roofs should not be considered a traffic area as it does cause issues with all products but cetainly one can take precautions in certain areas to provide for servicing of roof units/windows etc. Assuming that you still have the spaced sheathing in place I would suggest using a reinforced roofing underlayment such as Triflex 30, then strapping the roof vertically with 1.5" lumber centred over the rafters followed by the horiziontal strapping for the roof covering. Use a vented mesh at the eaves to intake air and similar at the ridge. Ensure that all pipe penetrations are taped to the underlayment. If possible choose an Energy Star Roof. If you want to upgrade your insulation in a vaulted assembly, then I would suggest ridgid insulation over the spaced sheathing, then the underlayment and counter battens etc. Best to use long screws to fasten the vertical battens. For areas that you may need roof access on use a 1" intermediate horizontal batten for those areas only. Check out our web site for energy star products at www.duraloc.com.
Guest User
2/5/2006
Thanks for the suggestion on Triflex 30. Have you ever heard about foam wedges between roofing and a plywood cover? I'm still trying to track these down. I did see a reference to them for Alcoa Aluminum shingles, but haven't been able to find any details. If you don't know Eichlers, then let me say that that are a bit "special". As I said in the original message, the roof (and I mean the entire roof) is tongue and groove 2x6 redwood. What this means is that the bottom of the 2x6 is seen from the inside of the house while the top side of the 2x6 currently has no insulation, tar paper and shakes. Not only that, but ceiling wiring was Romex placed under angle irons that were laid on top of the 2x6's (we're planning on redoing the wiring at the same time as the roof, and it's one of the reasons that we want to bump up the profile a couple of inches). On the each side of the pitched portions of the roof lies a flat roof made with the same design. There are no eaves from which to draw ventilation and I am still awaiting details from the contractors on how they would ventilate.
Allan Reid
Dura-Loc Roofing Systems, Inc.
2/6/2006
There is a company in the NW that makes a product called Wedge It however our company does not recommend it as we feel this type of application cuts off the air flow, increases condensation and has a net energy loss.
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