Effective moisture management is essential to prevent condensation risks, ensuring the health and comfort of a building’s occupants. Condensation risk analysis is therefore a key tool when designing and specifying building fabric elements, including floors, walls, and roofs.

Thermal insulation plays a significant role in minimising the potential risk of both surface and interstitial condensation. However, it must be specified correctly and, crucially, installed properly on-site.

When considering condensation risks, it is important to acknowledge additional factors influencing moisture vapour levels in a building, including:

• The level of airtightness achieved 
• Ventilation system specification and performance
• The number of occupants and their activities (e.g., frequency of showers, drying washing indoors).

The starting point for understanding condensation risks

A fundamental aspect of condensation risk analysis is determining whether a construction follows a vapour-open or vapour-closed approach.

Polyisocyanurate (PIR), glass mineral wool and blown insulation products may be specified as full and partial fill insulation solutions to improve the U-value of a masonry cavity wall. Choosing between full and partial fill installation and subsequently selecting the correct insulation type is essential in terms of compliance with Building Regulations and is crucial to the energy performance and the carbon footprint of a building. There is a variety of products available for full fill cavity insulation. PIR, glass mineral wool and blown insulation offer different properties and specification will depend on the client’s needs and building performance requirements. Full fill solutions are designed to prevent moisture movement through the cavity, eliminating the need for a clear cavity that is required when partial fill insulation products are installed. The distinctions between cavity insulation products available on the market are often subtle, but it is crucial that the right products for a project are selected to achieve optimum performance of the cavity wall insulation. All cavity wall solutions must have third-party certification, confirming they are fit for purpose. These solutions must also be specified and installed in accordance with the relevant certifications. We will now explore the benefits of PIR as cavity insulation in the context of full and partial fill installation.

How does rigid full fill cavity wall insulation work?

Traditionally, rigid insulation boards used in masonry cavity wall applications were offered only as a partial fill solution. Now, rigid full fill solutions for masonry cavity walls mean the clear air cavity can be significantly reduced or eliminated entirely.

By filling more of the wall cavity with thermally efficient polyisocyanurate (PIR) insulation, masonry cavity walls can achieve lower U-values with little or no increase in the overall thickness of the wall construction.

Using rigid full fill PIR cavity wall insulation to lower U-values

With a thermal conductivity as low as 0.021 W/m.K, a full fill PIR solution offers a more efficient way to insulate a cavity compared to partial fill solutions. It is also more thermally efficient than a corresponding full fill glass mineral wool product, making it ideal for projects that require both lower U-values and minimum wall thicknesses.

Masonry cavity walls featuring rigid full fill insulation products should be designed in accordance with the manufacturer’s details. For example, Thermaclass Cavity Wall 21 can be installed with a nominal 10mm cavity (which benefits from the low emissivity facing of the insulation board), or as a true full fill solution.

Using rigid full fill PIR cavity wall insulation to protect against moisture ingress

The use of perimeter upstand insulation is key to stopping heat escaping through the edge of the screed or concrete oversite in solid floor constructions.

This post aims to cover what a vapour control layer is, why it’s important and when it’s applicable to roof and floor applications.

Today, we are talking about another vital construction component called a vapour control layer, or a VCL.

At Celotex and our colleagues at Soprema UK’s Technical Department, our advisors are regularly asked questions relating to the VCL. What is it? What does it do? Am I using it the right way? With this in mind, our technical advisors have put together a VCL focussed FAQ post.

What is a vapour control layer (VCL)?

A vapour control layer helps you protect your building from the consequences of condensation. Condensation is formed when warm moist air penetrates the building fabric and then condenses into a liquid on contact with the colder surfaces outside the insulation layer. The idea behind a vapour control layer is to install it on the room (i.e. warm) side of the insulation so it blocks the passage of warm moist air entering the structure.

Why is a VCL important?

What is PAS 2030 and how does it apply to the Green Homes Grant?

Publicly Available Specification (PAS) 2030:2017 describes how energy efficiency measures in dwellings should be specified, installed and commissioned. It forms part of a network of standards and quality assurance measures intended to deliver high quality retrofit work.

The Green Homes Grant scheme requires that installers are certified to PAS 2030 to ensure the delivery of high quality of work throughout the industry. However, the scheme was launched at a time when the retrofit sector was moving from PAS 2030:2017 to PAS 2030:2019. A temporary transition policy has been announced by BEIS (the Department for Business, Energy and Industrial Strategy).

Essentially, Green Homes Grant work may be carried out under either Specification, apart from in certain defined instances where both PAS 2035 and PAS 2030:2019 must be used.

How does TrustMark registration fit with PAS 2030?

The Green Homes Grant scheme has created a surge of interest in domestic retrofit. To minimise the risks of poor quality work being carried out, the government has sought to incorporate quality management into the scheme and as such all businesses must be registered with TrustMark which requires a commitment to customer service, technical competence and trading practices.

The government has launched its new £2bn Green Homes Grant scheme. Through the scheme, eligible homeowners will be able to apply to help pay for the installation of energy efficiency measures such as thermal insulation, as well as new boilers, double glazing, draught-proofing and solutions such as air-source and ground-source heat pumps.

What is the Green Homes Grant?

The Green Homes Grant is part of a broader £3bn investment plan to cut greenhouse gas emissions across the country. It will help homeowners pay for home improvements that will boost energy efficiency whilst reducing energy bills and contributing to the UK’s target of net-zero emissions by 2050.

Up to 600,000 eligible homeowners will be able to apply for vouchers worth up to £5,000. These will cover up to two-thirds of the cost of the upgrades, with homeowners paying the balance. For some of the country’s lowest-income households, vouchers up to £10,000 may be available which could cover up to 100% of the cost up to the £10,000 voucher limit, with the remaining balance payable by the homeowner.

Depending on the home and the works carried out, it is estimated that the improvements could save households up to £600 a year in energy costs.

The £2bn Green Homes Grant scheme is a government-funded voucher scheme that helps homeowners pay for the cost of installing thermal insulation and other energy-efficiency measures in their homes.

As part of a broader £3bn investment plan by the government, the scheme was launched to improve the energy efficiency of the UK’s housing stock, contributing towards the goal of net-zero emissions by 2050. Its launch, amid the economic downturn caused by the Covid-19 pandemic, is hoped to give a boost to the economy, particularly the construction sector.

For contractors, the Green Homes Grant could be a welcome source of new work – but you’ll have to act quickly to ensure you are approved to carry out installations under the scheme.