Flat Roof Insulation Between Rafters

Batts between rafters in would require adding ventilation between the insulation roof deck.

Flat roof insulation between rafters.

This limits the maximum thickness of the insulation between the rafters to between 50mm and 175mm. Unless the joists are exceptionally deep there is also likely to be a requirement to install insulation to the underside of the joists as the upper 50mm of joist space is usually required to be left clear for ventilation purposes. An efficient room in a roof in a new build property where over rafter insulation is not desirable. The insulation is below the deck but above the plasterboard.

A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. This generally would not be a sufficient thickness to achieve the u values required to meet building regulations and more insulation would need to be added. Its versatility is the key to its popularity whether being used to achieve. It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains.

Arguably the most popular pitched roof solution installing insulation between and under the rafters uses the depth of the structural timbers to best effect. A cold flat roof is one where the insulation is between or between and below the roof joists. Hack n stack sealed foam board between the rafters would be better since it s at least an air impermeable insulation but even that would require a vent gap below the roof deck to meet code and you d still be under r38 on that 2x6 rafters unless you. This is used for refurbishment e g.

Https youtu be w4mkphzmqxw contact us restorat. Common rafter depths range from 100mm to 200mm. An over and between rafter insulation solution can be a feature of a new build project. Between and under joists.

If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters. With a warm roof the usual process is to split the insulation into two layers. Framing this out and buying 30 r fiberglass insulation will cost you about 50 more than just buying 5 inches of polyiso equivalent of 30 r. Time to get the insulation finished and get this place warm.

To protect the roof from the potential of condensation occurring unseen within the construction it s important to remember that the layer of insulation installed over the rafters should as general rule be double the thickness of the insulation layer between the rafters. Check out our how to video at the link below. Then install r 30 fiberglass batts between the rafters.