Roofing professionals emphasize that the choice of flat roof insulation should feature the appropriate R-value. The most expensive and highly recommended insulation is Polyisocyanurate (Polyiso) rigid foam. Extruded Polystyrene (XPS) is also an optimal choice, along with Expanded Polystyrene (EPS).
What is the best kind of insulation for a flat roof?
Flat roof insulation is used to enable a room to feel warmer in the winter and cooler in the summer months. Wood fibre, cellular glass and polystyrene (EPS or XPS) all have good insulation properties, but foam works particularly well and is often found in modern constructions.
How do you insulate a flat roof on a house?
Closed-cell polyurethane spray foam will prove ideal for thermal insulation of a flat roof. Such an insulating solution involves applying several layers of PUR foam, with each layer around 1–2 cm thick. The effective roof insulation layer may range in thickness from 3 to 12 cm, as needed.
How thick should flat roof insulation be?
A minimum thickness of 18mm is recommended. The contractor should ensure that it is suitable for the particular roof structure.
How do you insulate a flat cold roof?
Warm Flat Roofing: Insulation material is placed on top of the roof, rather than in-between the ceiling and the decking. Cold Flat Roofing: Insulation is placed in-between the joists underneath the roof surface above.
What is the most effective roof insulation?
Spray foam insulation
One of the most common and effective ways to insulate your roof is with polyurethane spray foam.
Can you add insulation to a flat roof?
Because most flat roofs don’t have an attic, crawl space or venting, the insulation must go underneath the roof’s covering on the exterior of the home or be placed on the inside of the home. If there is a small crawl space available, you can add insulation there.
How much does it cost to insulate a flat roof?
The average cost of insulation panels, the most common roof insulation, is about £25 per square metre, while spray foam insulation is at least £30 per square metre, so we would estimate that the average cost of roof insulation in a property would be about £400 to £500.
Do flat roofs need to be vented?
The article notes that the ventilation cannot overcome the significant humidity drive into the flat roof structure caused by small air leaks. Consequently the article concludes that the concept of venting a flat roof is no longer safe, and instead don’t vent the flat roof and install a smart vapor retarder inboard.
How do I stop condensation on my flat roof?
The cold deck solution
There are two forms of flat roof construction which can reduce the risk of condensation forming. Essentially, thermal insulation can either be placed above or below the structural roof deck or waterproofing layer.
Does a cold flat roof need a Vapour barrier?
2 Answers from MyBuilder Roofers
If it is not a habitable space or as per the old design for flat cold roofs then you would use foil backed plasterboard which acts as a VB. ideally you need to ventilate the roof and have a 50mm air gap above your insulation.
How much does it cost to insulate a warm flat roof?
To comply with Part L of the building regulations 2010, all roofs to rooms (except those in unheated buildings) should be thermally insulated to a maximum U-value of of 0.18 W/m²K.
Are cold flat roofs allowed?
Cold roofs must have ventilation. Warm roofs must have a VCL bonded to the deck. Roofs must be wind resistant and strong enough to walk on.
How do you ventilate a cold deck on a flat roof?
The cold deck roof as shown above has the insulation at ceiling level and must have a ventilated cavity of at least 50mm. The cavity must be ventilated on two opposing sides by a continuous ventilation gap of 25mm. A vapour control layer is required on the warm side of the insulation to combat condensation.
Which is better warm or cold flat roof?
A cold flat roof insulation requires more work, taking off old boards and replacing them and the roof surface. The thermal efficiency isn’t as good as with warm roof insulation. A warm deck roof is much easier to install, offers great thermal performance but adds height to the flat roof.
Which is better warm or cold roof?
A warm roof is the easiest and most cost effective type of insulation and is an ideal choice for pitched roofs. On some flat roof extensions and balconies, a warm roof would increase the height and isn’t possible, in this scenario you should choose a cold roof insulation.