Interior vs Exterior Wal Insulation

diagram showing how much heat escapes from wallsInsulating your solid walls could trim your heating costs considerably, because solid walls let through double the heat as cavity walls do. Thankfully you can insulate them.

If your property was built before 1919, its external walls are most likely solid rather than cavity walls. Cavity walls are made from two layers with a small gap or ‘cavity’ between each layer. Solid walls have no gap, so they let more heat through.

An alternate way to tell is by measuring the width of the actual wall. Take a look at an external wall window or door and if the brick wall is lower than 260mm, then it’s probably a solid wall, while if it’s greater, it is probably a cavity wall.

If you live in a property which has a non-traditional construction like a concrete, steel or timber-framed building, the insulation methods will differ. Learn more from the National Insulation Association.

Solid wall insulation

Solid walls can be insulated – either internally or the outside. This is going to be more expensive than insulating a standard cavity wall, but the financial savings on your heating system bills will be bigger also.

one vs the otherInternal or external insulation?

Internal wall insulation is conducted by fitting fitting the walls with rigid insulation boards, or by creating a stud wall filled in with insulation material like mineral wool fibre.

Exterior wall insulation will involve fixing a layer of insulation material to the wall, then covering it with a particular form of render (plasterwork) or cladding. The finish for rendering can be smooth, textured, painted, tiled, panelled, pebble-dashed, or finished with brick slips.

There are pros and cons to the two according to Premier Plastering in Birmingham:

Internal wall insulation:

  •  Is typically less expensive to install than exterior wall insulation.
  •  Will slightly decrease the floor area of any rooms where it is applied (the thickness of the insulation is around 100mm)
  •  Is disruptive, but can be done room by room
  •  Needs skirting boards, door frames and external fittings to be taken off and reattached
  •  Can make it tough to fix heavy items to interior walls – although special fixings are available
  •  Needs any troubles with penetrating or rising damp to be fixed first.

External wall insulation:

  • Can be applied without disturbance to the household
  • Does not reduce the floor area of the house
  • Renews the appearance of external walls
  • Improves weatherproofing and sound resistance.
  •  Fills cracks and gaps in the brickwork, which will reduce draughts
  •  Increases the life of your walls by shielding the brickwork
  • Reduces condensation on internal walls and can alleviate problems with damp (but will not eliminate rising or penetration damp)
  •  Is best installed at the same time as external refurbishment work to reduce the cost
  •  May require planning permission – seek advice from your local council
  •  Requires good access to the external walls
  •  Is not recommended if the exterior walls are structurally unsound and can’t be repaired.

Brandie Chapman