Good morning everyone, my name is Carol Michalak, and welcome to our sixth webinar of 2022. Our series of webinars has been running now since 2020, and if you’ve missed any you can go back and review them all on-demand right here on our YouTube channel.

You can also catch up on our learning hub at, where you can also book in for follow-ups with our team of experts around the country, access up to date information on our full range of products, or order product samples.

Today’s webinar is the third in our series of toolbox talks focussing on installation and site practice, and we’ll be looking at our range of Spacetherm aerogel insulation systems.

We’ll begin with an overview of the basics of thermal insulation and how it affects moisture movement in buildings.

We’ll then run though some frequently asked installation questions and common situations found on site.

Spacetherm Product Introduction

Our Spacetherm range of high performance thermal insulation systems are based around a silica aerogel matting, which is both hydrophobic and vapour permeable. Aerogel itself is a very low density solid that, so the story goes, was invented in the 1930s by the American chemical engineer Steven Kistler in order to win a bet.

An aerogel is a gel in which the liquid is replaced by gas without shrinking, via a complex process called super-critical drying. Raw silica aerogel is essentially puffed up sand, best described as being to sand what a rice krispie is to rice. The resultant structure is 97 percent air, entrapped in nano-sized pores, and while a superb thermal insulator, is very brittle, limiting it’s practical applications.

Our spacetherm systems use a modified for of this aerogel, which in impregnated into a fibrous carrier mat. This results in a flexible and robust material, with thermal conductivity of 0.015 watts per metre kelvin making it among the best thermal insulants in use today.

Because the aerogel insulation blanket contains no blowing agents it does not release harmful gasses into the building over time. Extensive testing has also showed no degradation in performance over a 50 year period.

Variants of Spacetherm aerogel are also available with reaction to fire classifications up to A2, making these products suitable for use in almost any situation.

We can supply this insulation in a variety of composite panels and systems to suit a variety of application in both new build and refurbishment projects, and we’ll disucss those shorty. First though, lets take a brief look at how insulation performance is quantified, and how thermal performance and moisture management are interlinked.



When we talk about insulation levels in buildings we generally refer to U-Values, which quantifies how fast heat flows through a specific part of the building, in this case we’ll consider a wall. U-values can also be referred to “thermal transmittance” and a lower u-value indicates better thermal insulation.

A typical solid brick wall of the type found in older building is across the UK, will usually have a U-value of 2.1 watts per metre squared kelvin. Compared to a new build wall, which will usually be in the region of 0.15 - 0.2 depending on what regulations you’re working to, this falls a long way short.

As we move towards reducing energy consumption address this shortfall in performance in older buildings is critically important, not least in terms of reducing fuel poverty and improving the indoor environment. We’ll come onto how poor insulation and poor health and linked later but first lets look at how we can upgrade such walls.


The u-value is calculated by taking the inverse of the sum of the total thermal resistance of the wall. This thermal resistance, or R-value, is measured in metres squared kelvin per watt and in our example wall here, 220 millimetres of solid brickwork with a plaster skim has a thermal resistance of 0.31 metres squared kelvin per watt, the inverse of which gives us our 2.1 u-value. Higher R- values indicate higher levels of insulation, i.e. more RESISTANCE to the passage of heat energy.

It’s also worth remembering that the relationship between u-values and R-values is not linear. As u-values get lower, exponentially more R-value is required to make a further improvement. So upgrading our example wall from 2.1 to 1, requires substantially less insulation than upgrading from 1 to 0.3.

If we want upgrade this to reach a u-value of 0.3, we must increase the R-value by 2.88. A u-value of 0.3 is the best case for upgraded walls given in approved document L for England and Wales, but similar values are given in Section 6 for Scotland and Technical Booklet F1 for Northern Ireland. Technical Guidance Document L in the Republic of Ireland looks for 0.35.

In all these cases however there are specific exceptions made if meeting these values is not technically or economically feasible, so the exact value can vary form project to project. To keep things simple for now though, we’ll stick to 0.3 for our example today.

Lambda Values

So what insulation has an R-value of 2.88?

R-value are calculated by dividing the thickness of a material in metres, by it’s thermal conductivity, or lambda value, which is measured in watts per metre kelvin. The lower the thermal conductivity, them better insulation a material provides.

Metal like steel have very high thermal conductivities, with stone and bricks being much lower, and timber even lower still.

Material that are used for insulation have thermal conductivities even lower still, with mineral fibre being between 0.035 - 0.044, polystyrene foam 0.032 - 0.038 and polyurethane and phenolic foams 0.018 - 0.025.

The aerogel blankets we use in spacetherm are between 0.015 and 0.019 depending on the fire rating requirements.

Taking the lowest value for each material we need the following thicknesses to get a R-value of 2.88. 100 millimetres for mineral fibre, 92 millimetres for polystyrene, 52 millimetres for phenolic foam and 44mm for aerogel.


Simply adding the R-value together to get a u-value doesn't tell the whole story though, as insulation layers may be placed between timber studs, or may be penetrated by fixings such as screws and nails. There may also be air gaps in the layers. All of these can affect thermal performance, so various correction factors are applied to the calculation to account for these.

The method for applying these corrections and the conventions as to how and when they are applied, are explained fully in the ISO 6946:2017 standard, and the BRE guidance document BR443:2019.

In most cases the easiest way to ensure calculations are done correctly is to use u-value calculation software. If you visit our website at we have a free online calculation tool available to registered users which can provide project specific calculations using data from an extensive library of building materials.

You can also save multiple calculations for a project, collaborate with other users in your team, and send you calculations for review by our experts before printing off fully compliant reports for building control. The calculator can also use postcode specific climate data to generate condensation risk analyses using the ISO13788 Glaser method.

The amount, type and placement of insulation in an upgraded wall can have a big effect on the condensation risk, and we’ll move on to disucss that now.


The management of heat and moisture in buildings are fundamentally linked, and any changes to the thermal insulation must also be assessed for their impact on moisture movement. Particularly in older building which use traditional materials and techniques like lime plaster.

The balance of heat and moisture flows in these buildings must be carefully considered, so now we’ll take a look at the interaction between heat flow and moisture flow.

In our solid brick wall example, without any insulation, the temperature within the wall decreases pretty uniformly from inside to outside. The heat in the building interior also pushes moisture through the wall, by means of vapour pressure. This pressure is created by the internal temperature and humidity.

As long as water vapour is kept above a certain temperature it will remain as a vapour and diffuse outwards through the wall, but if it cools below what’s called it’s dew point it will revert to liquid water. This process is what causes bathroom mirrors to mist up, or water droplets to form on cold drinks cans.

By comparing the dew point with the temperature gradient we can predict if, and where, there is a risk of condensation occurring in the building fabric.

Adding insulation to the wall will change this dynamic in two ways, firstly the temperature gradient will alter, with the temperature dropping through the insulation layer rather than the masonry. This also results in the brickwork of the wall becoming colder.

Secondly, the insulation will affect the way moisture can move through the wall, which in turn will alter the dew point.

An insulation which is highly vapour resistant, such as a foil faced PU foam, will limit the ingress of moisture from the heated space, and reduce the dew point through the wall. While this might seem to present an ideal solution, there is an important downside, and one which cannot be modelled using the ISO13788 method.


The Glaser method given in ISO 13788 assumes that moisture only flows from inside to outside, and that the indoor environment is the only source of moisture. It also omits the ability of the building fabric to store and release moisture. For most types of building, these effects do not significantly effect the results of a dew point analysis, but in the case of our solid example wall, they can play a greater role.

In a solid wall, moisture from rainfall is absorbed directly by the wall which can then store this moisture until it dries out. In an insulated wall, this moisture dries out outwards, driven by the internal heat sources, but also inwards, driven by warm and sunny summer weather.

So that high performance rigid foam insulation board has impacted both these processes, and heat form inside no longer drives moisture outwards to the same extend, and inward drying is also limited.

Because the aerogel blankets we use in the spacetherm products are vapour permeable, this inward drying can still take place, but this must balanced against the higher level of moisture ingress that a permeable insulation allows.

Our team of technical experts can use a more complex moisture analysis, using the methods form BS EN 15026, to model this process dynamically. This assessment can take into account the effects of weather and moisture storage as well as drying out in any direction.

This assessment can be used to determine what level of vapour resistance is optimal for a specifc project and vapour control measure such as integrated foil layers can be specified accordingly.


When upgrading building, it’s important to consider the effects of thermal bridging. We mentioned earlier how this can occur at fixings and where structural materials penetrate insulation layers, but maintaining the continuity of insulation is important in other areas too.

Door and window opening are a particular problem here, as it’s not always feasible to add a substantial thickness of insulation without encroaching on the window or door. It is however important to add as much insulation to these areas as possible.

Although it might seem like these areas will not significantly affect the overall heat loss, when insulation is added to the main parts of the wall, these areas will become colder than they were prior to the application of the insulation. This happens because less heat is able to reach the masonry wall through the upgraded insulation.

Because these areas become colder, it is more likely that a surface condensation risk will occur, where the warm, moist internal air meets the colder masonry. Insulating these areas, even to a lesser extent than the main wall, will help counteract this condensation risk, and it’s here that Spacetherm is particularly useful.

Even just 10mm of aerogel applied to these areas will make the internal surface temperature far more uniform, and warmer, leading to a significantly reduction in surface condensation risk.


There are a range of spacetherm systems available to fit more or less any project requirements. Most systems can be supplied in a variety of thickness and with or without integrated vapour control layers. Before we move on to discussing the installation processes, lets briefly review the range of systems and their applications.

The blankets of insulation can be supplied unfaced, for use a multipurpose high performance insulation blanket, and are also available with an A2 fire rating. The fire rated blanket can also be supplied as an option in the laminated systems to suit project requirements.


Firstly we have spacetherm wallboard, a straightforward, traditional plasterboard thermal laminate board. This is supplied in standard plasterboards sheet sizes, and is fixed to existing timber studwork or timber battens.

Spacetherm wallboard is supplied with an integrated vapour control layer, but this can be omitted on request, resulting in a fully vapour permeable board.


Spacetherm Direct fix takes the spacetherm wallboard laminate and adds a layer of robust plywood reinforcement to allows the board to be directly fixed to suitable solid substrates using shot fired fixings.

This removes the need to provide timber battens, hence saving further thickness, and is made possible by the hydrophobic nature of the insulation layers. Because Spacetherm aerogel does not absorb liquid water, it can be placed directly against masonry without additional damp proofing.


Spacetherm Multi replaces the plasterboard with a 6mm Magnesium Oxide facing board, proving a dual purpose board than is suitable for use in wall and floor applications. The boards are also available in 1200x2400 or 1200x600 panel sizes, for easier site handling on projects with restricted access such as loft conversions.

The inherent moisture resistance of both the spacetherm aerogel and the magnesium oxide facings make it a good option for floors where the presence or condition of damp proofing make be unknown.


Spacetherm Wall Liner comprises aerogel insulation bonded to a durable 3 mm Magnesium Oxide facing board and fixed in place internally using a gap filling adhesive. The panels can then be jointed, skimmed, then painted and decorated in the same way as a normal plasterboard wall.

It is supplied in a 1200 x 600 mm panel weighing just 4.9 kilograms, meaning that sheets are easily handled by one person and can be easily moved to hard to reach areas or stored onsite with affecting access.

Once installed, the system provides a significant reduction in heat loss with a minimal 13 mm increase in wall thickness, meaning in most cases sockets, switches and TV/network points can be left in-situ and features such as cornices and windowsills can be left as is, with no modification required.


Wraptherm combines the thermal performance of aerogel, and the low air leakage rates of our Wraptite air barrier membrane into one system. Sheets of wraptherm can be directly adhered to suitable substrates to limit both cold bridging and unplanned air movement in one process.

As Wraptherm is fully vapour permeable, it does not adversely affect the movement of moisture through stonework. This helps limit damage that can occur when moisture flow through older stonework is altered by upgrade works.

As well as protecting the existing building fabric, Wraptherm’s hydrophobic properties provide a secondary barrier to water ingress and by sealing tightly to door and window frames and other penetrations.


Designed to prevent cold bridging through a component or element of a structure. Spacetherm CBS (Cold Bridge Strip) consists of Spacetherm Aerogel insulation encapsulated in durable polyethylene. Spacetherm CBS is an ideal choice for timber or steel frame structures and on request, can be cut to a variety of widths to suit different applications.

In addition to timber and steel structures, it can also be used in other applications where cold bridging is an issue, such as concrete columns, foundation details and many others.


(From accompanying PowerPoint presentation here: )

This Webinar Includes
  • Spacetherm Product Overview
  • Benefits of Aerogel Insulation
  • Installation Best Practice
  • Site Conditions and Preparation