Could timber frame give you more space?

28 December 2018 Ian Loughnane

How using a market leading insulation within a timber structural wall can pay lifelong dividends.

Kooltherm K12 Framing Board Corner UK 09-13

Anyone considering building a new home quickly realises three things:

  1. The market value of your home is driven by the floor area (internal living space)
  2. The size of your home is limited by the plot and planning permission
  3. Space comes at a premium

Space = Value

The amout of internal floor area you build into your home is critical to its finished value. There are other considerations but the more usable space there is, the more it will be worth.

Given that a typical build cost can start from £1400 per m², it's easy to see how simply building bigger will inflate your budget.

Thankfully, there are ways to maximise floor space in a self-build project without breaking the bank. One smart way to do this is to use technology and advances structural systems to release extra space within the overall house plan.

By using a market leading insulation like Kingspan’s Kooltherm within a timber structural wall we can deliver high thermal performance in a slim wall build up - delivering more internal space!

When choosing a build system many ignore thickness and performance, with cost alone being used as the main criterion for selection. There are many systems to choose from, and building to reasonable levels of thermal efficiency isn’t difficult. However, if that performance is delivered without the benefit of high-performing insulation materials it’s almost certain that the overall wall will be thicker. This means less living space for a given external envelope.

By using a market leading insulation like Kingspan’s Kooltherm within a timber structural wall, we can deliver high thermal performance in a slim wall build up. This really can pay lifelong dividends.

To illustrate the point let’s look at some typical walls. Based on a brick external skin with a cavity let’s compare some systems that provide a U-value of 0.17 W/m2K inclusive of service zones and internal finishes where applicable.

Construction type Insulation type Wall thickness to achieve 0.17 W/m2K
Masonry (medium dense block) Cavity blown bead 435mm
Masonry (medium dense block) Cavity PIR board 380mm
Insulating concrete formwork (ICF) EPS permanent formwork 451mm
Timber frame Kingspan Kooltherm 312mm

What could you do with 9 square metres of “extra” space?

Extra Space Roundel

You can see that both structural material and insulation type have a very significant impact on finished wall thickness. For those seeking minimalist energy bills, the Kingspan ULTIMA system can deliver 0.13 W/m2K in the wall above at only 337mm!

So choosing a high-performing insulation could yield between 68mm and 139mm of additional space around the entire perimeter. On an 8m x 10m two-storey house, that means an internal floor area ranging from 129m2 to 138m2 with Kingspan’s Kooltherm-based system. What could you do with 9 square metres of “extra” space?

The Delivery of Advance Thermal Performance

The above examples deliberately simplify the description of thermal performance to a single characteristic, a “U-value” to avoid overly complex comparisons.

There are lots of paths that heat can escape along. To allow us to design out these paths, we use three energy performance measures: U-value, Psi Value and Air tightness.

A measure of how much heat escapes through a typical one square metre of a building element. So a floor slab, a wall, a roof or a window all have U value characteristics.
Heat also escapes through building junctions. Typical examples of junctions with Psi values are the perimeter of doors and windows, the junction between floors, roofs, ground slabs & the external wall. A Psi value measures the amount of heat that escapes through a junction per metre length. For a SAP calculation the Psi value calculation (which results in an overall building parameter called a “y value”) has a significant impact on the overall result.
Living in a leaky home is like living with a window permanently open. The more air tight a building the more warm air remains indoors longer.

Our systems not only uses industry leading insulation materials (Kingspan Kooltherm) with the best thermal conductivity performance when compared to other commonly available insulants but are designed to optimise performance when measured against ALL three parameters. It is on this basis that we claim that for an alternative system of the same “U value”, Kingspan Ultima will outperform an alternative build method by having better Psi, air tightness and thermal conductivity performance characteristics:

Ultima has a unique patented continuous Kooltherm liner and airtightness membrane which cuts the thermal bridging of the wall considerably not only within the U value derivation but also when thermally modelled at the Psi junctions.

The continuous VCL, protected from damage behind the Kooltherm liner, is air sealed at all the panel junctions with specialist tapes, foam and silicone to drive excellent levels of system air tightness. This means that you can control thermal leakage and improve the quality of the internal environment with the use of a mechanical ventilation and heat recovery system (MVHR).

Take the space test

See how much space you could gain - submit your drawings for your space gain result!

Kingspan Timber Solutions Ltd

Eltisley Road

Great Gransden


SG19 3AR

01767 676400