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How to insulate a period London home
Do you want your home to feel warm, dry and cosy?
Would you like to discover the best way to insulate your period property?
Are you located in London?
If so you’re in the right place.
Written By Greg Mathers
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Insulating your home has many benefits, not just for the environment but also for your wallet. Having the correct insulation for your period property can help to retain heat during the winter and keep heat out during the summer.
By insulating your home you will save money as less fuel is burnt heating your home. Reducing our reliance on energy is one of the main ways we can combat climate change. According to the Committee on Climate Change energy usage in homes accounts for approximately 14% of our UK greenhouse gas emissions.
Insulating your home is a win-win situation for all.
From choosing the correct insulation products to the location of your new insulation, we’re going to delve into everything you need to know about insulating your period property.
How to insulate a period London home
Insulating a period home in a dense historic city like London can be challenging. There are many issues to consider. Depending on the property, you may need to think about:
A loss of space, affecting the usability of rooms.
The loss of period details internally or externally.
Product compatibility and sustainability.
Conservation area restrictions, limiting what can be done externally.
Listed building constraints restricting external and internal changes.
Complex abutments resulting from party walls shared with adjacent buildings.
Every building project is unique and there are no hard and fast rules. Each situation should be carefully considered.
When considering any major refurbishment work, a thorough assessment should be undertaken to plan the retrofitting of insulation, ensuring that any work, which will be locked in for the foreseeable future, is making best use of the resources and opportunity offered by the refurbishment. Insulation is near impossible to retrofit later, especially if on the inside.
Product considerations
Performance, toxicity and lifespan are the key issues to consider with insulation. Over time, some installation types will lose performance as they degrade. They also release gases that are bad for your health.
Performance on its own is much more than just a u-value, the measure of how insulating a product is. Considerations of breathability and compatibility with other products, and its installation, all affect how well the insulation will perform. When calculating the u-value, a condensation risk assessment should always be undertaken.
Insulating products can be made from materials such as cellulose, cork, fibreglass, flax, hemp, mineral wool, polystyrene, polyisocyanurate, polyurethane, phenolic foam, sheep’s wool, straw, wood fibre and more.
If you are concerned about what goes into your building, a good question to ask is whether or not you would eat a meal off the product. Natural insulations are an excellent choice. They not only help maintain good indoor air quality, they also absorb and lock in CO2, trapping it in the building for many years to come.
In period homes, such as London Victorian terraces, solid brick walls are breathable and absorb moisture. It is critical to use compatible insulations and in the right locations. Doing it wrong can trap moisture and damage the building, particularly any timber elements..
Floors
Most period London properties have suspended timber floors, that is timber floor boards and joists with a ventilated void below. Air passing through vents in the external walls helps keep these voids and the timber structure dry.
Suspended timber floors
Upgrading a suspended timber floor with appropriate insulation and airtightness measures is a good start. However, maintaining airflow from one side of the void to the other is critical. Dwarf walls often support joists that do not span full length. Installing insulation that restricts airflow over dwarf walls can cause damp and structural damage.
Concrete floors
If undertaking major structural work, a replacement concrete floor might be necessary. Insulation can go above or below the structural slab as long as the junction details are appropriate. The embodied carbon of a concrete floor will be much higher than a timber floor, but the higher performance and robustness might prove more beneficial in the long term.
Extensions
Extensions can utilise suspended timber or solid concrete floors. Extensions with concrete floors must not restrict the airflow under suspended timber floors, as this could cause damp and rot.
Watchpoints:
Maintaining ventilation across voids under suspended timber floors.
Using compatible insulation to ensure moisture movement.
Consider embodied carbon, sustainability, indoor air quality.
Walls
Period London properties typically have solid brick walls. Insulation can be placed externally or internally. Internal insulation is best carried out in conjunction with major refurbishment works as it can be intrusive.
External wall insulation
Most of us wear our winter coats outside of other layers. For similar reasons, external wall insulation is preferable: Floor and roof junctions are simple, insulation is more effective, no space is lost internally.
If the installation does not wrap the entire building, such as at shared party walls, these junctions need to be considered to minimise thermal bridges.
Internal wall insulation
When external wall insulation is not possible, internal wall insulation is the solution. Junctions with intermediate floors are critical. Uninsulated floor voids can comprise up to 30% of the heat loss of the wall.
To avoid thermal bridges at the junction with party walls, some insulation should be added to the flank party wall.
If a loss of space is an issue, replacing existing plaster with a small amount of insulating render can make a significant improvement to a solid brick wall.
If internal insulation is not possible, due to a loss of space or period details, careful detailing and construction to improve air tightness of all junctions can significantly reduce heat loss.
Watchpoints:
Robustness of external insulation at ground level to avoid damage.
Water tightness of external insulation.
Continuity of the insulation and thermal bridges.
Embodied carbon, sustainability, indoor air quality.
Heat loss at junctions with intermediate floors.
Breathability and moisture management.
Roofs
Properties in London typically have timber roof structures. Insulation can be installed to the loft floor or roof structure, either above or below.
Loft insulation
For uninhabited loft spaces, loft insulation can be added to the ceiling of the upper floor. The loft space would remain ventilated to allow moisture out but careful attention must be made to ensure that eaves vents are not blocked.
Roof insulation
Much like with walls, roof insulation is best placed on the outside of the structure. Adding insulation on top of the existing roof structure, will raise the ridge and eaves lines of the roof. This could require planning permission. The insulation should be continuous with wall insulation and roof vents should be closed.
If this is not possible, insulation can be added to the underside of the roof structure. Similarly vapour open materials like natural installations are preferable for moisture management. This will result in a loss of ceiling height but a creative design should make good use of space.
Watchpoints:
Ventilation in cold lofts to allow moisture out.
Junctions with external walls to ensure continuity of the insulation.
Continuity and correct placement of air tightness and vapour control layers.
Penetrations in the membranes and insulation that can let moisture into the structure.
Waterproofing and flashings at junctions with parapets and party walls
Planning permission for externally roof insulation
Closing redundant eaves vents
Risks and other considerations
In conjunction with a retrofit strategy for insulation, an air tightness strategy must be considered. This is to ensure that the new “winter coat” is fully zipped up and no heat is lost from inside. This also ensures that moisture does not travel with escaping air which can condense and lead to mould growth, damaging the building and putting your health at risk.
Making a building more air tight, means that a new form of ventilation will need to be considered. Unmodernised traditional buildings are very draughty. This is what helps keep them dry. For more on this, you can read our article on indoor air quality.
Another risk of insulating a building is the potential for overheating in the summer. This heat might be from indoor occupants or from solar gain through the windows. Ideally, a whole house strategy should be considered during the design stages to predict overheating risks and mitigate them if necessary.
A comprehensive strategy is essential to ensure a sensible whole house solution.
Talk to us about your project.
I am passionate about how considered, well built, Passivhaus inspired homes can transform the quality of people’s lives. And I love talking about it so please get in touch if you want to learn more about its suitability, costs, processes, and what to expect. You can contact me to arrange a free consultation via my contact page.
