Roof Insulation and Its Benefits

When considering what insulation to place in your attic you should keep a number of factors in mind depending on what you want to do with the space. There are two options available to you; if you want to use the attic as a living space then insulating at the rafters would be of the most benefit to you. However, if you do not want to use your attic then it would be best to insulate at the ceiling or joist level otherwise the heat will rise through the uninsulated ceiling into the attic space and this will waste your heat and your money.

How Different Insulation Options Can Benefit You

According to professional roofing services, both of the options have some noticeable differences and you should be aware of each of them.

Rafter Insulation

  • If you are to insulate your attic at the rafters this will create a warmer loft space.
  • It may not be possible to install a thick layer of insulation between rafters so an additional layer of insulation may be required underneath.
  • As the loft space is warmer, it avoids the need for insulation on tanks and pipes in the loft space.

Joist Insulation

  • A thermal barrier is created by insulating at the joist level directly above your ceiling. This leaves the loft much colder, so the space can’t be used for anything other than storage.
  • Most homes are insulated at joist level because it takes less heat to warm the rooms below.
  • In insulating at the joist level there is an increased chance that piping or water tanks will be more liable to freezing now during the cold winter weather months. Steps should be taken to prevent this with insulated pipes or water tank jackets.

Fitting Insulation Between (or under) Rafters

Logik roofing North York would recommend fitting the insulation flush between the timber rafters to form a tight fit. Any gaps should then be filled with an expanding urethane sealant or flexible mastic.

Here’s a step by step guide as offered by a custom roofing company in North York.

  1. Measure the space between the rafters before cutting the boards as spacing’s vary
  2. Cut an insulation board to size using a sharp knife or fine toothed saw.
  3. Install the correct thickness of insulation while ensuring a minimum 50mm ventilated space is maintained between the insulation and the roofing felt.
  4. In all cases ensure that insulation boards between rafters are fitted tightly.
  5. Fill any gaps with expanding urethane sealant.
  6. Measure up before cutting the boards
  7. Cut the insulated plasterboard Insulated Plasterboard Board to size using a sharp knife or fine toothed saw.
  8. Where board dimensions allow, fix the boards at right angles to the underside of the rafters.


Boards should be fixed with dry-wall screws long enough to allow 25 mm penetration of the timber. Boards can be fixed at 230mm centres when using drywall screws and no less than 10 mm from the edges of the board along all supporting edges.