Air Gap Between Floor And Insulation

Even a small seemingly insignificant gap allows warm air from the house to leak into the attic.

Air gap between floor and insulation.

As part of a local council grant i am getting my attic floor insulation 2 inch thick fibreglass replaced with 4 inch thick insulation. I then plan on flooring the attic not as a living space but for storage. It will lie between the joists on top of the plasterboard which forms the ceiling of the rooms below. Walls often have air spaces hidden somewhere between the siding on the outside and the drywall on the inside.

Some are accidental some on purpose even code required some served a purpose at one time in history but because of the evolution of construction are no longer useful some are wasteful and some can cause damage. As the joists are 2x4 s this. Seal the gap between the bottom plate of the wall and the floor with acoustical sealant or caulk. Insulation can t do its job if it s not completely filling the voids between the joists.

4d extend insulation into joist space to reduce air flows. This is because these unventilated gaps actually contribute to the thermal performance as still air is a good insulator. 4c as an alternative to floor insulation foundation walls of unvented crawl spaces. Use special airtight electrical boxes see photo tip 5 or seal the poly to the electrical box with acoustical sealant.

Air gaps larger than this work well too they promote ventilation on the foil and help keep the air dry and the air temps lower. The number one attic insulation mistake is leaving gaps and spaces between and around the insulation. Buy unfaced friction fit batts and seal the walls with a 4 mil poly vapor retarder. A minimum 10 mm gap between the membrane and tile slate batten although 15 mm is typical to maximise thermal performance.

A lot of people have been telling me that when installing insulation it is necessary to leave a bit of an air gap between your outer wall and your insulation in order to allow for air flow. Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. After years of answering questions on this web site i. If your building is built to nhbc standards then a ventilated 50 mm gap is still required.

On a continuous surface for example laid flat on the insulation or sarking board. Just a comment on the air gap behind the stud wall. How much of a gap has never really been specified which is also confusing because i understood that bat insulation was sized to fit the entire 3 5 inch. In situations where you have a breather membrane in place over insulation between the rafters although the tile batten space over the breather membrane needs to be ventilated any gaps below should not be ventilated.

Also insulate 4a any portion of the floor in a room that is cantilevered beyond the exterior wall below.