Flat Roof Insulation Between Rafters

Breathing roof with low resistance lr underlay with this option insulation fully fills the rafter space without an airspace between the insulation and type lr underlay.

Flat roof insulation between rafters.

Pitched roof rafter level. The general advice we give is that you should always insulate between and above the rafters or between and under the rafters on our u value calculator we don t give an option for putting insulation between the rafters. Kingspan with a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. Is there any advantage to trying to get any insulation in between the 2 8 rafters.

A cold flat roof is one where the insulation is between or between and below the roof joists. Should i leave out the soffit vent. Refurbishing an existing timber joisted flat roof which has no insulation. On new build or replacement pitched roofs the ideal build up would be insulation fitted over and then between the rafters giving a big boost for airtightness image credit.

A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. No ventilation is required for these types of roofs. The old roof was tar and gravel so the switch to tpo should show significant change. I have an insulation factor of about 8 10 plus the reflectivity of the white tpo.

An over and between rafter insulation solution can be a feature of a. Where the insulation does not fill the total rafter depth the low emissivity foil facings can gain additional thermal benefit from the air spaces they face. Also there is a soffit vent but none at roof peak. It allows insulation to be installed in a watertight roof either after the roof covering has been fixed on a new build or without disturbing an otherwise sound existing roof covering as part of a renovation.

Being lightweight they do not impose significant additional loads on existing structures. The underside of the rafters in this case will need to be finished with a suitable vapour control layer vcl and plasterboard to provide a suitable internal finish to the roof. Insulation between the rafters can be designed in two ways. In this blog post we will be looking at insulating pitched roofs and why putting insulation just between the rafters isn t a viable solution.

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. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings. Modern u value targets mean installing insulation between rafters only is rarely a viable option. The insulation is below the deck but above the plasterboard.