How To Add Insulation To The Outside Of A Roof

Another few inches isn t really going to do it.

How to add insulation to the outside of a roof.

This video shows you how to use knauf insulation rock mineral wool rmw for sarking insulation installed above rafters and covered with homeseal lds weather. That s much more common these days than it used to be but not accepted by everyone. At that point what you are doing is building a r e m o t e wall read more about that here. Installing insulation that acts as a vapour barrier on the outside will not serve you well except if you add enough of it to the point where about 2 3rds of the total insulation is on the outside.

It would probably be easier to insulate from the inside and add false architectural elements if you have the headroom of course. You have an un vented roof. At that point what you are doing is building a r e m o t e wall read more about that here. If adding insulation to the outside roof is prohibitively expensive then the alternative is to add it to the inside.

George and his team insulates a roof from the outside in with two pound closed cell polyurethane foam in a residential attic. Installing insulation that acts as a vapour barrier on the outside will not serve you well except if you add enough of it to the point where about 2 3rds of the total insulation is on the outside. Placing this vapor barrior on the outside of the wall the coldest place in the wall in winter can cause this vapor to condense at a location where it cannot be seen until it begins to cause serious mold or wood rot. Adding exterior foam on an old roof is a good idea whenever a reroof is planned it is a once in 50 year opportunity to bring the house up to higher level of energy performance.

4 strap with 2x4s and then i was considering cross strapping with 1x4s to help create better cross ventilation as on the back of the roof there are skylights and then the front has two valleys see attached pic. If you decide to add rigid foam insulation to the ceiling inside you ll have to nearly fill the rafter bays to get a layer of sufficient thickness. 3 add r31 of foam to roof to create the correct inside to outside ratio of insulation as currently there are faced r30 fiberglass batts on the interior of the rafter bays. Or ripping off the existing metal roof and adding the insulation on the roof deck.

At any rate the problem is creating your air and thermal barrier at the existing metal roof plane. The insulation this article recommends is a vapor barrior which would prevent the vapor from migrating out of the house. Because old roofs were often framed with 2x6s there isn t much room for insulation.