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.
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).
In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below. If the air distribution is in the attic space, then consider insulating the rafters to move the distribution into the conditioned space.
Yes, an air gap between the roof and insulation is needed, especially for traditional materials like fibreglass, mineral wool, and foil insulation.
So if you are insulating a pitched roof, we would recommend having insulation either above or below the rafters.
Moisture control is an important consideration when it comes to insulation between rafters. Insulation materials such as mineral wool, glass wool, and rigid foam boards can help to control moisture by providing a barrier that prevents water vapour from penetrating the building envelope.
Where the distance from the top of the braced wall panel to the top of the rafters or roof trusses above is between 91/4 inches (235 mm) and 151/4 inches (387 mm), blocking between rafters or roof trusses shall be provided above the braced wall panel in accordance with Figure R602.
Overall, the second layer of insulation plays a crucial role in improving insulation performance, reducing heat loss, and maintaining a comfortable and energy-efficient living space.
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.
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.
While it may seem like the more insulation you have, the more energy-efficient your home will be, you do not want to insulate both the attic floor and ceiling. Insulating the floor and the ceiling would create a separate and conditioned environment, especially if you air-sealed your attic.
Best roof insulation for roof rafters
Place insulation material between or over the sloped structural beams (rafters) to insulate the roof. Creating a thermal barrier, roof rafter insulation keeps interiors warm in winter and cool in summer, benefiting living spaces.
Fiberglass batt is considered to be the best insulation for attics. Compared to other insulation materials, it is the cheapest and easiest to install.
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).
Should You Insulate the Attic Floor or Roof Deck? If you are looking for an insulation upgrade that you can see (on your energy bill) and feel (in a home that is more comfortable), we recommend insulating the attic floor, and using radiant barriers on the roof deck.
In roofs, the air gap should be larger, typically around 50mm (2 inches), to allow for proper ventilation and prevent condensation. It's important to note that some insulation materials, such as spray foam, do not require an air gap.
It's important to leave a ventilated air gap between the insulation and the boards to prevent condensation on the underside of the boards.
If a heating or cooling system is installed in an unfinished attic, insulate the rafters to convert the area into a conditioned space. In a finished attic room or dormer, insulate between the rafters and studs of your exterior wall for better temperature regulation.
One important thing to remember is that insulation should never be pushed right into the eaves because it will interfere with airflow. If you're going for a warm loft then you'll need much more insulation to be able to cover the underside of the roof along with the gable and party walls.
The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.
Generally speaking, vapor barriers are considered an essential moisture-blocking tool for climates that experience significant levels of humidity. For that reason, building codes in more humid locations will often require them, in which case you might not have much say about whether to install one or not.
ABOUT INSULATION
The thermal barrier of a home should consist of a continuous layer of insulation on all sides—including the lowest floor, the exterior walls, and the ceiling or roof. Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half.
Blanket insulation
It comes in rolls or batts and is installed between the roof rafters. This attic insulation is effective at reducing heat loss and can be a cost-effective option for insulating your roof.
Outrigger. An outrigger is sometimes called a "lookout". These are pieces of wood installed perpendicularly across rafters, from the common rafters in past one roof rafter and secured into the next.
Each space between the rafters needs a baffle, and you must fit each one snuggly into the bay.