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TOPIC: Insulation Concerns

rigid insulation

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I am looking to install a metal roof over an existing fiberglass shingle roof that is in good condition but nearing the end of its life. I plan to use a PBR or Tuff-Rib profile panel attached to a grid of vertical and then horizontal battens, creating an airspace beneath the metal which will be vented. I have also thought about adding some type of radiant barrier along with insulation to improve energy efficency of the roof system. I have looked at the bubble / foil insulation and dont think the product looks that durable but found a rigid 1/2" insulation board with a foil radiant barrier on one side that looks good. My thought is to fill in between the vertical battens before installing the horizontal ones, leaving about a 1" airspace between it and the metal roofing. Any thoughts or advice would be appreciated, and any thoughts on how much of benefit this would be.
Guest User

6/10/2008
I would not completely fill in the vertical battens. You wnat to get upward unobstructed airflow between the vertical battens for maximum effectiveness. Bring air in at the bottom and exhaust out through a ridge vent.
Todd Miller
Isaiah Industries, Inc.

6/11/2008
I thought of even using a 2x4 for the vertical batten and a 1x4 for the horizontals. That way with either 1/2" or 3/4" rigid insulation there would still be 1"+ free air space. Any ideas of performance gains with using an insulation and radiant barrier?
Guest User

6/11/2008
A radiant barrier on top of the insulation, pointing upward, would be helpful.
Todd Miller
Isaiah Industries, Inc.

6/11/2008
Todd, Are you recommending an additional radiant barrier, or just that the foam insulation should be oriented such that the wide with the foil radiant barrier is on the roof panel side (as opposed to the decking side)? Alice
alice gilbert

6/19/2008
The latter but do not encapsulated the radiant barrier in a tight "sandwich" of materials. It must face an airspace or else it will conduct heat.
Todd Miller
Isaiah Industries, Inc.

6/22/2008
We have a metal roof, with a layer of what appears to be tar paper underneath on top of plywood, soffet vent around the perimeter of the house eaves and at the south end a vent and at the north end another with a thermostatically controlled fan. All works fine but the attic floor has spotty free insulation, I'm thinking of adding the hard foam radiant barrier 4X8 sheets with foil facing upwards as a barrier which when attached to the roof trusses will provide a 4" airgap. I intend to stop short of the interior roof peak which should flow hot air up to the electric fan where it would be exahusted. Thought's?
Guest User

6/27/2008
That sounds fairly good.
Todd Miller
Isaiah Industries, Inc.

7/13/2008
Greg, I'm looking at doing something similar in AZ. Here are some things I have found. 1. A video on You Tube showing an installation of 2" foam over an exiting roof then a installing the Standing Seam Metal Roof. No Gap or Radiant barrier. Just shows that it can be done. 2. Prefabricated Ridged Insulation with air gap and decking. Several manufactures are selling this and most allow you to specify air gap, insulation thickness, and decking material (thickness and type). As of now I'm unable to determine if they use a radiant Barrier or not. I'm sure it is pricy, but it will save time. This link lists some of the MFG's http://www.4specs.com/s/07/07-2200.html Comments - 1. When I do my roof I'm going to pull the existing roof to ensure my decking in good shape. 2. From my research this is an excellent way to reduce the heat load in your attic space. No one has done this exact installation but it is putting several practiced good ideas into one job. Do you plan on recording the benefits of this type of installation? It would be interesting to see some number. 3. I also plan on putting 4x8 pieces of Foam over the entire roof then installing my batten system over this. This will ensure there is an even insulation value across the entire roof. Questions - 1. How are you going to vent at the eves? 2. What type of attic ventilation are you doing with this?
Guest User

8/31/2008
I am going to try and document my installation but it wont be until after the first of the year before I get the chance to do it. I am putting a remote thermometer in the attic to doucument tempatures before I change the roof. You can do some checking on "above sheathing ventilation" and find more info of different ways to accomplish it. Currently I have "standard" attic ventillation with soffit vents and a ridge vent which I will keep and add some type vented closure material for the metal roofing.
Guest User

9/2/2008
Thanks.
Todd Miller
Isaiah Industries, Inc.

9/5/2008
Great thread. I think that you should consider foam insulation. It has a very high R value [6 per in]. I got it installed in my home and saved about 40% on my bills in the winter.
Guest User

10/20/2010