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Building insulation

The Regulations Building regulations are in place to drive improvements in thermal efficiency, these regulations apply to new build, renovation or replacement work.

  • England & Wales: Part L Building Regulations 
  • Northern Ireland: Technical Standard F1
  • Scotland: Technical Handbook Domestic, Section 6 (energy) 

Thermal efficiency within these documents is expressed as a U-value.


Put simply, a U-value is the measurement of the rate of heat loss through a material. So in all aspects of home building and renovation customers should strive for the lowest U-values possible, the lower the U-value, the less heat will be unnecessarily lost.

The calculation of U-values can be quite complex. It is measured as the amount of heat loss through a 1m2 of material for every degree difference in temperature either side of the material. However, Siniat are here to help.

HOW TO Calculate U-Values

Download our free Siniat Calculator App from the Apple or Android stores or contact one of our Technical Services Team who will help calculate your required U-value for you.


1. What type of construction is the wall/roof of your project? Or what age is your property?

2. For walls/roofs
– What is the construction of the wall/roof outside to in?
– What insulation products are in the wall/roof?
– Do you know the hermal values of these products?
– What U-value do you need to meet?

3. Building address (needed for calculating the condensation risk).

Siniat Technical Services team can be contacted between 9am – 5pm Monday to Friday on 01275 377 789

How to select your thermal board

Choosing thermal boards

Thermal Boards

Controlling Condensation

Adding additional insulation layers to a building to prevent heat loss, helping the environment and lowering heating bills is, of course, a good thing, however there are some challenges.

When you apply internal insulation to an external wall, the wall becomes colder. This creates a danger that vapour from inside the home will get trapped behind the insulation, and as it cools it can condense on and inside the wall fabric, in the same way that you get condensation on the surface of single glazed windows. This invisible condensation inside a wall is called interstitial condensation.

This condensation can lead to substantial problems of damp, mould and rotting of timber elements. Siniat GTEC Thermal PIR and Thermal K Boards have a metallised vapour barrier provided as standard, the vapour barrier sits between the plasterboard and foam layers.

The vapour control layer helps prevent the passage of warm moist air from inside the property from permeating into the wall structure or into the roof space, where it can condense and cause damage.

thermal boards with vapour layer

How To Install using Dot & Dab Method

Thermal board can be installed by either Dot and Dab or Dryliner method. The Dot and Dab method should only be used for walls that already include a cavity.

1. Starting from a window, door reveal or internal angle, mark the wall vertically with a chalk line for the row of dabs.

2. Using Siniat Universal Bonding Compound place a continuous ribbon 50mm at the top and bottom of the board.

3. Then place your dabs on the wall making sure that they are 250mm x 75mm in size and at 300mm centres.

4. A maximum spacing of 400mm horizontally should be used. A continuous ribbon should be placed around any plug sockets or light fittings.

5. Press the plasterboard in place against the dabs fitting the board tightly against the ceiling using a wedge or off cut at the base.

6. Tamp the board into place with the floor and ceiling chalk lines using a straight edge.

7. Use two Nailable Plugs to suit board depth, fitted through holes drilled in the board through the dab cavity and penetrating 25mm into masonry.

(Tip: Wait until the dabs have set before fitting plugs to avoid moving or bending the board.)

8. Remove wedges when compound

How To install with drylining

Thermal drylining installation

1. Fix a dryliner track at 600mm centres to the floor and ceiling using suitable fixings. Allow for required cavity of at least 25mm.

2. If applying direct to concrete make sure that the surface is dry and a damp proof membrane.

3. Mark vertical lines at 600mm horizontal centres to fix the dryliner channels.

4. Start at the centre of the wall and position the dryliner brackets directly to the wall at a maximum 800mm vertical centres on the marked lines (at shoulder and waist height).  Secure using suitable fixings. Fold out the toothed wings of each bracket to form legs.

5. Cut each dryliner channel 5mm shorter in height from the floor to the ceiling and place into the dryliner track.

6. Ensure channel is plumb and secure to each bracket using a Pan Head Self Tapping screw.

7. If installing kitchen units, install a GTEC fixing channel or timber reinforcement at the height the wall and floor units need to be secured.

8. Cut plasterboard 5mm shorter than the floor to ceiling height. Butt the board firmly against ceiling and fix with GTEC

Drywall Self Tapping screws at 300mm centres. Screws must be at least 10mm longer than the board thickness.

9. Butt the plasterboard edges lightly against each other and centre the edges over the channels.

NOTE: Cannot be used for cavities over 130mm.


One of the main areas of heat loss is through the roof. This installation guide will demonstrate how Thermal Board can be installed to meet required thermal performance. Installing the board and insulation at the same time using a laminated board is less time consuming and easier than separate installations.


1. Remove any existing plasterboard if present.

2. Install the required thickness of glass mineral wool or solid foam insulation between the rafters, joists or trusses ensuring no gaps.

3. Using the required thickness and type of Thermal Boards fix to the wooden rafters, joists or trusses using Siniat High thread screws, the screws need to be the total thickness of the board plus at least 25mm to penetrate the timber.

4. Screws to be fixed at 150mm centres around the perimeter and cut ends of the boards and 230mm centres in the centre of the boards.

Loft insulation

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