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Insulating an unvented low-slope roof

abrace | Posted in Energy Efficiency and Durability on

Been reading through many articles throughout the web discussing the varied approaches to insulalting different roof types in varied climates with various materials. that said I cant seem to find (or may have overlooked) approached to insulating my roof.

I live in Washington DC and here’s what I have:

Flat roof comprising of (bottom to top):
2 x 8’s;
Plywood strips;
2 x materials ripped to provide slope, laid on top of the plywood strips and installed to create a valley in each corner of the roof;
5/8″ CDX;
2″ thick Isoboard;
Heavy gauge black EPDM attached by glue down to the Isoboard

Installed an ERV where each bathroom is the exhaust point (Exhaust Air To Outside)

I’m considering installing Spray Foam against the interior of the CDX and have heard the pros and cons of open vs closed.

And here’s where I may get my self into trouble……I love can lights and want to install them regardless of the solution I install.

I’m reasonably well read on basic insulation theories and would appreciate the opinions of any senior (experience not age. though they are somewhat related) bloggers or experts that are familiar with my scenario or one’s close to it.

Many thanks in advance,

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  1. GBA Editor
    Martin Holladay | | #1

    1. You should never install recessed can lights in an insulated roof assembly. For more information on this topic, see Ban the Can.

    2. Here is an article that should explain everything you need to know about insulating this type of roof: Insulating Low-Slope Residential Roofs.

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