Insulation Between Rafters Flat Roof

Modern u value targets mean installing insulation between rafters only is rarely a viable option.

Insulation between rafters flat roof. Refurbishing an existing timber joisted flat roof which has no insulation. 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. Also there is a soffit vent but none at roof peak. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow.

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. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings. 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. Alternatively battens can be secured to the underside of the joists and gmw fitted between these in much the same way as between the main roof joists.

This is used for refurbishment e g. Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. 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. Box out light fixtures.

Being lightweight they do not impose significant additional loads on existing structures. Should i leave out the soffit vent. 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. 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.

The old roof was tar and gravel so the switch to tpo should show significant change. For example if the space beneath the rafters is going to be used for a living area then you will need to insulate the roof rafters. A cold flat roof is one where the insulation is between or between and below the roof joists. Water is insulation s enemy.

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. I have an insulation factor of about 8 10 plus the reflectivity of the white tpo. The insulation is below the deck but above the plasterboard. An over and between rafter insulation solution can be a feature of a.

Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be.