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How to Insulate a Detached House

Choosing the Right Insulation for Detached Houses

As with any installation, insulating a detached house first involves choosing the type of insulation that you want to use. This decision can depend upon a number of factors, whether it’s based on the thermal performance of the material or how suitable it is for your particular property. Here are the salient points for each of our insulation materials:

Kingspan K5

  • Thermal conductivity: 0.020 (W/mK)
  • This is much more expensive than EPS, but a lesser thickness is required to reach the same U-values (60mm of K5 vs. 90mm of EPS). Great for if you are lacking external space.

EPS (Expanded Polystyrene)

  • Thermal conductivity: 0.032 (W/mK)
  • Cost effective, lightweight and with excellent performance. Our most popular insulation board.

Mineral Wool

  • Thermal Conductivity: 0.036 (W/mK)
  • Manufactured by Rockwool, our Mineral Wool insulation is completely non-combustible, breathable and with acoustic insulating capabilities.

XPS (Extruded Polystyrene)

  • Thermal conductivity: 0.038 (W/mK)
  • More expensive than EPS, but with better compressive strength and greater resistance to water. Installers tend to use XPS for insulating below the DPC, with EPS above the DPC.

Insulating the chimney breast

With a detached house, you’ll often find that the house has a chimney breast that will require externally insulating. If the chimney breast is in-use or is likely to be in the future, then it needs to be insulated using Mineral Wool insulation. This is because Mineral Wool is completely non-combustible, so when the chimney gets very hot during use your external wall insulation system remains completely safe.

Extending the Roof Line

Whether it’s detached or semi-detached, many installations involve extending the roofline to ensure that the roof adequately overhangs the insulation. If this isn’t the case, verge trim needs to be used to ensure that the system is completely watertight.

Verge trim is installed underneath the soffit to extend the overhang of the roof and ensure that water runs directly off the front of the system, rather than running down the back. If water manages to get behind the system it can cause serious damage, which needs to be avoided. Verge Trim is, therefore, an essential item to prevent this.

Insulating Above a Porch Roof

Detached houses often have a porch roof or a secondary roof where there is a ground-floor extension. On these properties, lead flashing tends to be applied to the area where the wall meets the roof. When insulating a detached house that has a porch roof, it’s essential that the lead flashing is re-installed on top of the insulation to prevent water gathering underneath where the insulation meets the roof. The lead flashing will enable the water to run directly down the wall and off the roof without causing any issues.

Insulating Bay Windows

If you’re insulating a detached house with a bay window, there are a few ways you can do this. Unfortunately, starter track isn’t designed for bay windows, but you can adapt your uPVC Starter Track to fit the bay window by cutting slits in the base so that it will bend to fit the wall.

Sometimes the bay window sill does not have enough of an overhang in order to house the EPS insulation. In this situation, you have two options: you can either extend the window sill so that the EPS will fit underneath, or if the window sill is wide enough you can use a 60mm Kingspan K5, which will offer the same thermal performance as the EPS.

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