Do you need to leave a gap between roof and insulation?

Author: Miss Vanessa Schowalter  |  Last update: Wednesday, July 16, 2025

Should you leave a gap between the insulation and the roof? Yes, you should leave an air gap between the insulation and the roof to allow proper ventilation and prevent moisture buildup.

Should there be a gap between insulation and roof?

When it comes to insulation, it's generally recommended to leave a gap between the insulation material and any other surfaces, such as walls, ceilings, or roofs. This gap provides ventilation and prevents moisture buildup, which can lead to mould and other problems.

Can you put insulation directly against a roof?

You can put all the insulation on top of the roof deck, all the insulation on the underside of the roof deck, or some on top and some below. You can put it all below the roof deck but use two different kinds. Your insulated roof can be a cathedral ceiling or it can be above a conditioned attic.

How much space do you need between insulation and roof?

To maintain airflow, leave a space of 38 to 50 mm (1 1/2 to 2 in.) between the top of the insulation and the underside of the roof sheathing.

What is the clearance between insulation and roof?

Not less than a 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent.

Why you SHOULD pre-insulate your camper van in FOIL? - NO Air Gap & 13 Degree Difference?!?

Can insulation touch the roof?

Yes it can touch. As long as there is nothing obstructing flow from the soffits - which sounds like the baffles are.

What goes between roof and insulation?

A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.

Can you put too much insulation in a roof?

Yes, too much loft insulation can cause dampness in some situations. Loft insulation works by trapping warm air inside a building, preventing it from escaping through the roof. This helps to keep the interior of the building warmer in cold weather, reducing the need for heating and saving energy.

Should you insulate between roof 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). On our U-value calculator, we don't give an option for putting insulation between the rafters.

Is 2 inches of insulation enough?

The recommended thickness for attics is typically 12-16 inches. Spray foam insulation: As discussed earlier, the recommended spray foam insulation thickness can vary depending on factors like climate and location. For attics, a thickness of 2-4 inches is usually sufficient.

Should I insulate the underside of my roof?

Do you have any plans for furnishing/fitting out your attic in the future? Then you could simply insulate the pitched roof. But the best solution is actually to insulate both the attic floor and the underside of the roof.

Can fiberglass insulation touch roof sheathing?

Most building codes (including the International Residential Code) allow just one exception to these rules: in Climate Zones 2B and 3B, you can install fiberglass insulation against the underside of your roof sheathing without a ventilation channel or rigid foam above the sheathing — but only if you install tile ...

Does roof insulation need ventilation?

But it's not the only important player that helps keep you comfortable throughout the changing seasons. In addition to having proper roofing insulation, your attic space must also have an effective roof ventilation system that maintains a flow of ambient air throughout.

Does roof insulation need vapor barrier?

(Source: NRCA.) In the event you are erecting a “cold building” (such as a refrigeration building) that stays at 32 F (0 C) degrees or less inside, you will need a vapour barrier on the outside of the insultation to prevent warm exterior air from entering and potentially damaging the roof's insulation. (Source: NRCA.)

What is the minimum air gap for insulation?

You can't simply leave a gap between your insulation and the surface and call it a day. This is where sizing comes in, and it varies depending on the material used and where it's installed. It's recommended to leave an air gap insulation of at least 25mm or 1 inch for the walls and ceilings.

Should there be a gap in my roof?

Ideally, there should be a small gap between the drip edge and fascia to allow for proper water drainage and ventilation. However, this gap should be minimal to prevent water from infiltrating behind the fascia board, leading to water damage and rot.

Do you need a gap between insulation and roof?

Yes, an air gap between the roof and insulation is needed, especially for traditional materials like fibreglass, mineral wool, and foil insulation. The UK's Department for Business, Energy & Industrial Strategy's guide highlights the need to ensure proper ventilation in roof spaces to avoid moisture buildup.

When would attic insulation be placed between the roof rafters?

Warm Roof: Insulation is placed between and above the rafters. This method keeps the entire roof structure warm and minimizes the risk of condensation. Cold Roof: Insulation is placed only between the rafters, leaving the roof space cold. This method requires excellent ventilation to prevent moisture buildup.

What is the cheapest way to insulate roof rafters?

Foil insulation

Single or multi-layer rafter insulation foil is an aluminium-based membrane that is both affordable and easy to install onto roof rafters.

How much air space between insulation and roof?

Remember that a two-inch breathing space between the insulation and the roof sheathing must be included to allow for ventilation. If I leave room, it's hard to fit more than R-13 without going to rigid foam board.

Is it okay to cover attic insulation with plywood?

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

How much of a difference does roof insulation make?

Roof and ceiling insulation. Installing roof and ceiling insulation can save up to 45% (or more) on heating and cooling costs.

Should insulation touch the roof?

Insulation that touches the rafters provides better coverage and reduces the risk of heat loss. By creating a tight seal between the loft insulation and the roof, energy efficiency is improved, resulting in lower energy consumption and reduced utility bills.

Can you insulate between roof joists?

Insulating between the joists of your loft will keep your house warmer, but make the roof space above colder. This means pipes and water tanks in the loft space could be more likely to freeze, so you will need to insulate them.

What is the proper way to insulate a roof?

For traditional pitched roofs, sometimes called sloping roofs, you will be looking at three main options to insulate from the inside; installing solid insulation boards between the joists of your roof, installing fibreglass or mineral wool insulation batts within the joists, or installing spray foam insulation on your ...

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