Can we cover the electric wires and pipes in our attic with insulation?

I recently had an assessment for attic insulation, which included a spray-foam option, carried out by a reputable contractor. However, he was unwilling to comment when I expressed concern about all the electrical wiring and plumbing, which is strewn across the attic joists in all directions, being covered and literally buried under insulation. Am I right to be concerned, or, when it comes to services and insulation in the attic, are there standards or is it a question of “out of sight, out of mind”?

Pat McGovern writes: Considering that a quarter of a house's heat loss is through the roof, insulating an attic makes sound economic sense. However, you have raised a very valid question with your contractor, and he should not gloss over the matter. It is critical that electrical wiring and plumbing pipes are properly managed during any attic insulation job.

There are some basic commonsense rules that need to be followed. Obviously the first step is to completely clear out the attic. To have effective insulation you shouldn’t be storing items on top of it. Consider a walkway platform or shelving if you need the storage space and take care not to affect the structural integrity of the roof timbers.

Pipes cannot be covered lest they be walked upon and damaged while you search for your Christmas tree. All electrical cables should be clipped in place and secured. When laying the insulation, take care not to impede any ventilation openings at the eaves. Condensation is a risk in any attic and ventilation is key to managing this.

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There are two options when it comes to insulating an attic: insulation along the sloped section of the roof (between the rafters) or insulation between and over the floor of the attic (ceiling joints).

If choosing the roof option, the underside of the roof can be sprayed with foam insulation (applied to the felt and rafters). The advantage of insulating the rafters is that you insulate the entire attic space while leaving the floor free for storage and so on. The downside is that it will take more heat to warm the house due to the greater house volume to be heated as the attic space is now included. Care needs to be taken to ensure the roof timbers remain ventilated. To prevent water ingress, be sure to repair any tears in the felt before insulating.

If insulating (or upgrading your insulation) at ceiling-joist level, heat covers should be placed over any spotlights in the ceiling below. Take care also to ensure that any bathroom fans are not covered over. These must be vented to the exterior using a flexi pipe connected to a slate/tile roof ventilator.

If there are a lot of services cabling/pipes at ceiling level, you might need to consider running counter battens over the ceiling joists which would mean the cables can stay in place undisturbed. This will, however, have the effect of reducing the head space of the attic.

Don’t forget your water-storage tank, insulate around it but not under it. Lag all pipes servicing the tank.

Prior to getting the upgrade done I suggest you get professional advice from your local surveyor, architect, or engineer. At minimum, have an electrician inspect the space to make sure the wiring is safe and tidy. The SEAI website is a useful source of information on the grants available and there is a downloadable guide to attic and rafter insulation, seai.ie.

Pat McGovern is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland, scsi.ie