Adding rigid insulation to roof??

[Betty_B]

I contacted a roofer about putting a white coat put on our roof, in an attempt to reduce heat levels on the second floor in the summer (we have a typical two-story, flat roof, row-home in Fairmount). I was told that we actually need a new roof. They suggested using a smooth rubber coat, or a white granulated coat. Our existing roof is basically a faded silver coat. It seems to me that a new silver coat or white granulated coat alone would not do much in terms of addressing the heat issues. (It's not like we have a black roof now and we'd switch to a white roof.)

To address the heat issues, the roofer said that we could add rigid insulation to the job. He acknowledged that this can be pricey, but effective. An alternative would be to have insulation blown in above the ceilings (though I have no idea if we have a crawl space, how big it is, or what). I'm nervous about opening up another can of worms if we went with the blown in insulation route).

So, is adding rigid insulation to the roof a good idea? Something to stay away from? He didn't say anything about removing any of the existing roof, so I'm also wondering about what type of additional weight the insulation would add and if I should be worried about the load on the roof. I have no idea how old it is or how many layers are already up there.

Thanks in advance for any advice.

[HomeInspectorBC]

Hello Betty B amd Happy Monday,

My experience is that blow in insulation in the space between the your interior ceilings and roof framing is the preferred method as this helps keep the heater heat in the house and the summer heat out of the house. In a row home unless the second floor ceilings have been elevated there is typically a space between your ceiling joist and roof rafters and as long as there is not any knob and tube wiring in this space the insulation contractor should be able to add the insulation through the roof top instead of dragging his equipment through your house and making holes in your ceilings.

Adding insulation on the rooftop is typicically called a built up roof cover and is generally used for commerical applications and although it will make the house more energy efficient then not having the ridgid insulation, I belive the biggest bang you will get for your buck will be the blow in insulation. The rigid foam insulation will not add any significant weight to the roof cover unless it gets wet and retains water. Why dont you ask the roofer how many layers of roof covers you have on the roof as too many layers/weight on the roof can cause structural issues for the rafters especially with the added weight of heavy snow that is going to be staying on your roof longer now that your home will become more energy efficienct. Now if there is still active knob and tube above the ceiling space then the rigid foam maybe the way to go. Why don't you get some prices both ways and then make the best decision you can for yourself.

Thank you for your time and good luck with your home improvement project,

[Betty_B]

Thank you for the quick reply.

I wasn't aware of the knob and tube issue. I don't know if there is active knob and tube wiring, but I wouldn't be surprised if there was. Although we had some work done on the house when we moved in eight years ago, we did not have anything done with the wiring on the second floor (I've been meaning to get an electrician out to add some outlets anyway).

So perhaps the best way to proceed is to have an electrician come out and determine whether there is knob and tube on the second floor, then get some quotes on blown in insulation? From what you've said, I would need to have the blown in insulation installed prior to the roof work. (I like the idea of having the blown in insulation added from the roof, rather than from inside.)

[ACretin]

That silver/white coating is nothing but a band-aid anyway.

Tear that sucker off, it probably consists of 20 layers, weighs 5 tons and has never been removed since the house was built in 1880 or so. Everybody always wants to put another layer on, but you're only supposed to have 2 layers maximum.

Blow in insulation, and use the rigid layer as well under a new roof, it's not that much more. Run new electric when it's off.

[Moonraker]

Over 10 years ago, I elected to go with a rubber roof, from John P Donnelly 5525 American Street.
After removing 6 roofs including the original tin, they installed 3" rigid foam beneath the rubber.
The original coating was white, now they use a silver. I asked and there were at least 5 grades of silver coat, this one not available at Big Box stores, only roofing supply houses such as Stellwagen.

I have ever regretted it, and noticed a more comfortable summer sleep immediately. When I bought the house, I blew rock wool insulation to cover the lathe & plaster crossbeams. I guess I could add more bat, but need to determine that sometime.

[ACretin]

GAF makes both torch-down and glue-down white bitumen roofing rolls, then you don't need to silver coat your black rubber roof. I'm not sure the silver coating is designed for rubber roofs, but you don't need it if you're replacing your roof, because you can just put down a new already-white roof.

http://www.homedepot.com/Building-Ma...&storeId=10051

Ivan is cheaper usually
http://www.ivansupply.com/store/pc/I...ng-Supply.html

[Betty_B]

Roofer #1 came back with a quote for the rigid foam insulation part of it, and it was almost as much as the original quote for the new roof. He suggested going with blown in insulation instead, then putting on what he called a granulated white rubber. He didn't give me a good reason for not removing the existing roof, other than they usually don't do that/need to. If the quality of repairs/work done in the rest of the house prior to our ownership is any indication, I suspect there are many layers of roof already up there. So I need a better explanation there. Stupid question, but how do they tell how many layers there are? Do they literally just start peeling back a section?

I have Roofer #2 stopping by tomorrow (hopefully). I'll use all this info when speaking with him.

Thanks for the advice.

[HomeInspectorBC]

They will take a core sample to determine the number of layers are on the roof. It takes less then 5 minutes and they can seal the opening temporarily until the roof is replaced. Most roofers just want to slap something on top, make their money and roll because tearing the roof off is labor intensive and adds to the cost of the job.

Good luck,

[Ronnie]

Ask them to analysis the cost/savings of the roof over its entire life cycle. In today’s market some roofers will give you a report for free.