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Internal Wall Insulation

This page gives you a quick overview of all of the components you’ll need for a successful installation of our systems.

Target U-values

We have several systems for internal wall insulation, depending on whether the walls are flat or not and how thick you want it to be. The first is the UdiIN 2CM system which is super slim and ideal for surfaces that are fairly soft, in areas with limited space. At 30mm including the plaster layers, this is our thinnest insulation but will still bring U-values down to around 1.0 W/m²K and massively improve internal comfort.

The second system is the Pavatherm Profil system which is designed for flat surfaces and comes in 40 and 60mm boards giving U-values down to 0.6 W/m²K. 

Next, from 80 – 120mm the UdiIN system is perfect for flat surfaces. Our final system is the UdiIN RECO system which is designed for uneven surfaces such as historic brick or stone walls and also for uneven, part timbered surfaces. This system goes from 80 to 200mm in thickness and will achieve U-values down to 0.18 W/m²K.

With internal insulation it is important to check that no driven rain is penetrating the walls. For walls whose external surfaces are regularly hit by the weather you may need to consider external render or water repellent treatments to ensure the walls remain dry once insulated. Contact us to discuss this further if you’re concerned.

Whichever system you’re choosing you’ll need to decide which thickness of insulation boards you’ll need to use, this will depend on your target U-value. Once you’ve chosen your boards and calculated how many you need add 5-10% for waste, depending on the complexity of the walls.

Unless the wall is perfectly flat you’ll need to apply a thin layer of levelling render to the wall first. If the wall only requires a single layer up to 15mm to flatten then the Baumit RK38 lime render will be suitable. If you need thicker layers the Baumit RK39 lime render will be more suitable.

Once you’ve calculated how many boards you need, you’ll need to calculate the number of fixings required. If you’re fixing back to masonry you need the UdiASSEMBLY Masonry fixings for historic or soft substrates. High density substrates hold fixings better and so the Ejot STR-U fixings can be used or if on to timber then use the UdiASSEMBLY Timber fixings or the Ejot STR-H fixings. For either type of fixing you’ll need at least 6 per m².

Uneven wall surfaces

If you’re choosing the UdiINRECO system choose the thickness that meets your U-value target. Its also worth checking the level of variation that you get in the surface of the wall as each board can only accommodate a maximum of 20% of it’s thickness. The boards go up to 200mm so will cope with 40mm variation in the surface and take your U-values down to 0.18 W/m²K. We recommend you allow 5-10% waste and assume that each board is roughly 1m².

The rest of the system

All the openings in the surfaces of the above systems need to lined with reveal boards. These help form neat reveals and also reduce thermal bridging around the openings. You’ll need to use these boards to line the heads, sides and sills (if possible) of all openings. Remember to include the full thickness of the insulation and the depth of the recess of the window. The reveal boards are 1300 x 800mm and are glued in place with the UdiSPECIAL ADHESIVE or the system plaster if on to masonry. This adhesive is also required for any external corners.

Next you’ll need to look at all of the beads and trims. Around all of the openings you’ll need the UdiREINFORCEMENT internal render edging strip, allow for the same linear meterage as the reveal boards above. UdiREINFORCEMENT corner protection profiles are needed for the whole perimeter of windows, the heads and sides of doors and also for any external corners. Allow four of the UdiREINFORCEMENT corner reinforcement patches for each window and two for each door.

Finally you’ll need the plaster to finish the systems off. The UdiMULTIGRUND plaster is the base coat for the UdiIN and UdiIN RECO systems and is applied at 4mm thickness with a half-round knotched trowel. The UdiIN 2CM system or the Pavatherm Profil system can use the Baumit RK 70 or the Baumit StarContact base coat plasters. Each 25kg bag should cover around 3.5m².

Finally, the surfaces are finished with either Baumit Kalkin Glatt or Baumit RK 7 0N. The Klima Glatte is the finest finish plaster and will cover up to 10m2 per bag at 1-2mm. The RK 70 N will cover around 6-7m² at 1-2mm.

If you have any questions, contact us.

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Overview

Back to Earth is a natural building material supplier. We're not your typical builders'​ merchant though and instead work closely with our clients during the planning, designing and building phases of projects.

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