Do you need an air gap for roof insulation?

An air-space between the insulation and the bottom of the roof sheathing is desirable. … Without a proper air-space to allow the insulation and roof to dry out, this water will collect, potentially leading to rot and mildew.

How much space should be between roof and insulation?

When you use solid insulation board to create a warm loft the key thing to remember is ventilation – you must keep a 50mm gap between the roof and the rigid insulation board. We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe.

Does foil backed insulation need an air gap?

Do you need a 25mm air gap under the membrane? Although this is often considered standard practice, it is not a requirement; the important thing is that the drape in the breather membrane (which allows any water getting through the tiles to channel down to the gutter) should not be pushed out.

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Do you need an air gap with Kingspan?

The timbers must be deep enough to allow the desired thickness of Kingspan Kooltherm K12 Framing Board to be fitted between them along with a 25 mm (min.) air gap between the insulation layer and the brick wall. … Once the boards are installed, Kingspan Kooltherm K118 Insulated Plasterboard can be fixed to the battens.

Does spray foam insulation need an air gap?

If you want to use closed-cell spray foam, install felt paper in each stud bay, up against the back of the siding, before spraying. (Open-cell foam is also an option, but it must be at least 3 in. … air gap between the back of the siding and the felt.

What is the best insulation for pitched roof?

EcoTherm’s thin PIR insulation boards are ideal insulation for not only pitched roofs but loft floors, ceilings and dormer cheeks. EcoTherm’s rigid insulation boards will easily and quickly achieve required thermal standards in pitched roofs without the need to alter the thickness of the construction or your method.

Can insulation touch the roof?

The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams, and the material will block that flow. For the same reason, insulation shouldn’t touch the roof’s underside. Staple plastic or foam baffles to the roof sheathing, near the eaves, to keep the material away.

Is foil insulation any good?

Reflective foil insulation, as the name states, reflects the radiant heat, which is very important if you know that over 70% of heat loss and gain within the building envelope comes from radiant heat transfer. This makes this type of insulation very useful both winter and summertime.

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What is the best foil insulation?

10 Best Foil Insulation Boards

  • SuperFOIL. …
  • Dripex. …
  • SuperFOIL. …
  • SuperFOIL. …
  • SuperFOIL. …
  • SuperFOIL. SFBA MP Bubble FOIL LOFT Insulation Aluminium 2 x FOIL 1 X Bubble. …
  • Yuzet. 1.2m x 25m Yuzet Double Aluminiumised Bubble Insulation Foil. …
  • SuperFOIL. SuperFOIL SFBA MP 600mm Wide – Bubble Foil Insulation (0.6m x 25m)

Can you double up foil insulation?

You can either install a single layer or multiple layers of foil insulation, and you can mix it with other products.

Should there be a gap between insulation and plasterboard?

you should lave a 20mm gap between the kingspan in the rafters and the sarking boards and a 20mm gap between the kigspann and the plaster boards.

Should I insulate between rafters?

The general advice we give is that you should always insulate between and above the rafters (warm roof) or between and under the rafters (cold roof).

Does Celotex need Vapour barrier?

You must use a vapour barrier otherwise warm air, which contains more water than cold, may get through to the cold outer fabric. If it does, and cools, you’ll get condensation.

What are the disadvantages of spray foam insulation?


  • The upfront cost is higher than conventional insulation.
  • Payback period is 2-4 years.
  • It is not generally a Do-it-Yourself project.
  • The installation process is longer.
  • The process could be messier.

Where should you not use spray foam insulation?

When NOT to Use Spray Foam Insulation

  1. For areas that are too close to electrical boxes:
  2. For areas too close to ceiling light boxes:
  3. Open-cell spray foam on your roof:
  4. For closed-cavity spaces:
  5. If you have a history of skin, respiratory, or asthma problems:
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How many years does spray foam insulation last?

The International Association of Certified Home Inspectors states that spray foam insulation, wrap tape and housewrap insulation can last for more than 80 years. At the same time, cellulose, loose-fill, foamboard, loose fill and rock wool insulation can last up to 100 years.

Roofs and roofing