Loft insulation is key to making your loft conversion warm and energy-efficient. Our expert guide covers the best insulation types and vital maintenance tips to keep your loft performing well - you’ll find all the insights you need to make the right decision.
Proper insulation is a cornerstone of any successful loft conversion. With adequate insulation, the loft space may meet essential comfort and efficiency standards, leading to various issues that can compromise the usability and value of the converted area.
Below are the key reasons why insulation is crucial for loft conversions:
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Here, we cover different insulation types you can use in your loft conversion to ensure you insulate correctly. Click on each type to understand the pros, and the cons of each material to help you make a measured decision:
Rigid insulation boards offer top-notch thermal efficiency and support for your loft.
Pros:
+ High Thermal Efficiency: These boards have low K-values (0.022-0.027 W/mK), insulating well with a thinner layer.
+ Moisture Resistant: Many are foil-faced, adding a vapour barrier to keep out moisture.
+ Adds Structure: They provide extra rigidity when fitted between rafters or joists.
Cons:
- Environmental Impact: Made from petrochemicals, they have a bigger carbon footprint and can release harmful emissions.
- Expensive: They cost more than other types of insulation.
- Hard to Fit: Their rigidity makes them tricky to install in tight or irregular spaces.
Flexible insulation like mineral wool offers an affordable, easy-to-install option, especially for odd-shaped spaces.
Pros:
+ Easy to Install: You can easily cut and fit it into awkward spaces.
+ Good for Soundproofing: It absorbs sound well, making your loft quieter.
+ Budget-Friendly: It’s usually cheaper than rigid insulation.
Cons:
- Less Efficient: With K-values around 0.038-0.044 W/mK, you’ll need a thicker layer to match the thermal performance of rigid boards.
- Environmental Concerns: Producing materials like fibreglass is energy-intensive and less eco-friendly.
Thermal lining boards save space while providing insulation and a finished interior surface.
Pros:
+ Space-Saving: They insulate without taking up much room.
+ Easy Installation: You can install them quickly, often combining them with plasterboard.
Cons:
- Moderate Performance: K-values are typically between 0.020-0.030 W/mK, which is good but could be better.
- Costly: They are pricier per square metre than other insulation types.
- Limited Use: Best for tight spaces rather than large-scale insulation projects.
Wood-wool insulation is an eco-friendly choice that breathes and helps regulate temperature.
Pros:
+ Eco-Friendly: Made from natural wood fibres, it’s biodegradable with a low environmental impact.
+ Breathable: It allows moisture to escape, reducing the risk of condensation.
+ Thermal Mass: It stores and slowly releases heat, helping keep your loft comfortable.
Cons:
- Lower Efficiency: With a K-value of 0.038 W/mK, you’ll need more of it to insulate well.
- Cost and Availability: It can be more expensive and harder to find than other materials.
Recycled newspaper insulation is an eco-conscious option that offers good thermal performance and added fire safety.
Pros:
+ Eco-Friendly: It’s made from recycled materials, reducing waste.
+ Effective Insulation: With a K-value of 0.035 W/mK, it insulates well.
+ Fire Resistant: It’s treated to be fire-retardant, which boosts safety.
Cons:
- Moisture Issues: It can absorb moisture, so it needs a vapour barrier to stay effective.
- Settling: Over time, loose-fill recycled newspaper may settle, needing a top-up.
Hemp quilts provide a natural, breathable insulation option that’s easy to handle but less thermally efficient.
Pros:
+ Sustainable: Hemp grows fast and is environmentally friendly.
+ Breathable: It lets moisture pass through, reducing condensation risks.
+ Safe to Handle: Hemp quilts are non-toxic and don’t require protective gear during installation.
Cons:
- Moderate Efficiency: With a K-value of 0.039 W/mK, it’s not as thermally efficient as some other materials.
- Higher Cost: Hemp insulation tends to cost more than conventional options.
Sheep’s wool insulation is a breathable, eco-friendly material that provides solid thermal and soundproofing benefits.
Pros:
+ Breathable: It naturally regulates moisture, keeping insulation effective.
+ Eco-Friendly: Renewable and biodegradable, it has a low environmental impact.
+ Good Insulation and Soundproofing: With a K-value of 0.038 W/mK, it insulates and reduces noise well.
Cons:
- Expensive: It’s one of the pricier insulation options.
- Pest Risks: Wool can attract pests if not treated, though most products are now treated to prevent this.
The total average cost of insulating a loft conversion, considering material, installation, and additional costs, can range from £21.50 to £37 per square metre for materials.
With daily installation costs averaging between £175 and £450, and additional work adding an average of £150 to £467.
Considering these factors, the overall cost of your loft insulation project will vary based on your space's specific requirements.
Here’s the full breakdown of the insulation types, installation, an additional costs when insulating your loft:
What you need to understand about the legalities of preparing and installing new loft insulation in your new conversion.
TA U-value measures how well a building material, like insulation, prevents heat from escaping; the lower the U-value, the better the material keeps heat inside.
To make your loft energy-efficient and meet UK regulations, your insulation must hit a U-value of 0.16 W/m²K.This can be achieved with about 250-270mm of mineral wool insulation or an equivalent thickness using materials like PIR boards.
If your current insulation has a U-value worse than 0.35 W/m²K, you must upgrade to meet this standard.
If you renovate more than 25% of the roof, the insulation must comply with current Building Regulations.
For lofts with insulation worse than a U-value of 0.35 W/m²K (about 125mm of mineral wool), you’ll need to add more insulation to meet the 0.16 W/m²K standard.
As well as these legalities, there are a few more fundamental considerations to consider when installing insulation into your new loft conversion; here are three considerations from our building experts at LoftCompare:
