Should I insulate between roof rafters?

Author: scraper  |  Last update: Monday, September 7, 2026

Yes, but only if you are converting your attic into a conditioned, livable space. If your attic is purely for storage, you should never insulate the roof rafters. Instead, insulate the attic floor joists to keep your home’s main living space, and let the attic itself remain ventilated.

Is it worth insulating between roof rafters?

Insulating between roof rafters is not only okay, but it is often recommended as a way to minimise the use of headspace while maintaining comfortable indoor temperatures.

What is the best insulation to use between rafters?

One of the most popular and effective options for insulating between loft rafters is mineral wool, which is made from natural materials such as rock. It is also non-combustible, which makes it a safe choice for insulation.

How to insulate between roof rafters from inside?

Insulating roof rafters from the inside is best accomplished by creating a "warm roof" (unvented) using closed-cell spray foam or a "cold roof" (vented) using rigid foam boards (like PIR/Kingspan) or mineral wool between and under rafters. A 1–2 inch air gap must be maintained for ventilation if not using spray foam to prevent condensation.

Where not to put loft insulation?

Insulating your loft will keep your house warmer but make the roof space above colder. Without their own insulation, pipes and tanks could freeze and an uninsulated loft hatch could let cold draughts into your house. However, don't insulate underneath your water tank, because this can cause your water to freeze.

Why shouldn't insulation go between roof joists?

Do mice like blown in insulation?

Mice are curious and always searching for safe, snug, and warm nesting sites. Attics filled with blown-in insulation provide an excellent option–from the mice's point of view. As long as there is a ready food source. Mice are omnivorous and will eat and chew on almost anything including wood and electrical wires.

Should loft insulation touch the roof?

No, you should not lay loft insulation on top of the boards. This can compress the insulation and reduce its effectiveness. It can also create a condensation risk, damaging the roof timbers. The correct way to insulate your loft is to lay the insulation between the joists.

What time of year is insulation cheapest?

What time of year is Insulation cheapest?

  • Winter (December – February): High Demand, Higher Costs.
  • Spring (March – May): Moderate Demand, Competitive Pricing.
  • Summer (June – August): Peak Demand, Higher Costs.
  • Fall (September – November): Best Time to Buy and Install.

Can I touch insulation with my bare hands?

While you can physically touch fiberglass insulation with bare hands, you should never do it intentionally. Fiberglass is made of spun glass fibers that break off easily. Touching them causes microscopic glass shards to embed themselves in your skin, leading to severe, irritating itching, and sometimes a rash.

What not to do when insulating an attic?

Batt Insulation:

Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from recessed "can" lights, unless they are rated IC (Insulated Ceiling).

Why do banks not like spray foam insulation?

Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.

How much does it cost to insulate a 2000 sq ft attic?

Insulating a 2,000 sq. ft. attic costs between $2,000 and $9,000, with most homeowners paying around $3,600 to $5,800 for professional installation. The wide price range depends on the type of insulation, labor rates, and whether old insulation requires removal.

What to put between rafters?

Rigid Foam Boards

Made from materials such as polyisocyanurate or extruded polystyrene, these boards are ideal for homes that require high R-values but have limited space between rafters. Unlike fiberglass, rigid foam doesn't absorb moisture and provides consistent insulation performance over time.

What is the 25% rule in roofing?

The 25% Rule in roofing serves as a guideline for both homeowners and contractors when planning roofing projects. Basically, it means that if more than 25% of your roof's surface needs repairs, it's often wiser to contemplate a full replacement rather than patchwork.

Why are buyers walking away from homes with spray foam insulation?

Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.

Are loft rooms cold in winter?

In winter, lofts often become the coldest room in the house because heat can escape quickly through the roof if insulation is lacking. Without proper insulation, including additional measures like insulating the loft hatch, it can be hard to keep a converted loft warm in winter.

Can the lungs get rid of fiberglass?

Yes, your lungs can get rid of fiberglass, but how effectively they do it depends on the size of the fibers and where they end up in your respiratory tract.

Does loft insulation need to breathe?

Flat ceilings can be insulated using rolls of loft insulation. Installers should also insulate around dormer windows and make sure there's enough ventilation between the insulation and the roof. This helps stop moisture building up, which could cause problems later.

What insulation can you not touch?

Fiberglass insulation is formed into batts, rolls, and loose-fill insulation. Fiberglass is treated with chemicals to make it less flammable. These chemicals are known to be a harsh toxin and irritant to lungs and skin.

Do rodents like foam board insulation?

Foam insulation is a common target because it's easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation. But mice aren't just interested in chewing for the sake of it—they're also drawn to the warmth and shelter insulation provides.

Should I replace 50 year old insulation?

Home insulation doesn't have an “expiration date,” and the material doesn't “go bad” after a certain number of years have passed. Ultimately, the condition of the insulation and its performance are more important factors than age when deciding whether to upgrade or replace insulation.

What is the cheapest but most effective insulation?

When balancing upfront cost and overall thermal efficiency, the cheapest and most effective standard insulation is fiberglass batt insulation. However, if you are looking for long-term savings through superior air sealing, dense-pack cellulose often provides the best overall value.

Can you lay insulation over electrical wires in an attic?

Yes, you can lay standard insulation over modern electrical wires (like Romex) in your attic, but it must be done carefully to avoid fire hazards and comply with electrical codes.

What is the healthiest insulation for your home?

The healthiest, non-toxic insulation for your home is natural sheep's wool or hemp insulation. These materials contain no chemical binders or formaldehyde, actively regulate indoor humidity to prevent mold, and do not off-gas.

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