Typically, code requires 2 inches between insulation and roof sheathing. If you have 2x8 rafters, they are 7-1/4 inches deep, subract the 2 inches and that leaves you with 5-1/4 inches allowed for insulation.
You can insulate but you need to leave a gap between your insulation and the roof to allow the air the circulate. If you don't, your shingles will become very hot in the summer and they will prematurely get broken.
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.
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.
Yes it can touch. As long as there is nothing obstructing flow from the soffits - which sounds like the baffles are.
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.
Insulation is often laid in contact with the roofing felt. Where the felt is impervious any contact condensation will run down the felt and make the insulation damp.
A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.
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.
WALLS & CEILINGS
For example, in walls and ceilings, it's recommended to leave an air gap of at least 25mm (1 inch) between the insulation and the surface. This allows for ventilation and helps to prevent moisture buildup.
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 ...
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.
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.
(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.)
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.
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 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.
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.
As a general rule, insulation should be replaced or retrofitted every 15 to 20 years. However, it may need replacing or retrofitting sooner depending on the type of insulation installed, the R rating of the original insulation, compression and movement over time, and whether any damage has occurred.
Roof and ceiling insulation. Installing roof and ceiling insulation can save up to 45% (or more) on heating and cooling costs.
Underlayment. The underlayment is a moisture-resistant material placed between the decking and the shingles to help protect against moisture.
If the roof covering or roof membrane is a material of high moisture resistance or impermeable, then the building regulations require a 50mm wide ventilation gap beneath the roofing felt and tiles.
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.
Uncovering the risks: foam roof insulation
One of the most frequently underestimated dangers is the potential fire risk associated with foam insulation materials. Foam insulation is highly flammable and can ignite at relatively low temperatures, posing a significant threat to the safety of your home and loved ones.