Hemp Block Insulation – Less is Now Officially More!

Unity Lime and The Hemp Block Company are excited to announce a major step forward in Hemp Block construction.

Independent testing has shown that our hemp blocks have an improved thermal conductivity of 0.044 W/m·K, confirmed by our partners at Senini.

In practical terms, this means better insulation from a thinner wall, using less material whilst resulting in lower overall cost. Yes…….Less really is now more! 

 

Wood Fibre, Hemp Blocks & What this Means in Practice

• A 240 mm thick wall (hemp block with wood fibre) can now achieve a U-value below 0.18 W/m²K*

• A 300mm wall can achieve 0.14 W/m²K*

These figures highlight the exceptional performance of natural building materials, proving that sustainability and efficiency can go hand in hand. At Unity Lime we supply not only sustainable insulation products, but complete insulation systems which have been designed by our in-house Chartered Architectural Technologist. Have a look at our main Hemp Block/Wood Fibre Systems here – But don’t hesitate to get in touch with us if this is something you are considering, our technical team are here to guide you every step of the way!  

*prior to wall finishes. 

 

Why Less is Now More

• Less material means lower costs and reduced embodied carbon

• Thinner walls free up valuable internal space

• More performance improves comfort and reduces energy use

This step forward shows how hemp block construction continues to deliver high-performing, low-impact buildings without compromise.

 

Why Choose Hemp Block Insulation?

100% natural materials
Made from the woody core (shiv) of the hemp plant combined with hydrated lime, hemp blocks are completely natural. The hemp captures carbon dioxide as it grows, and that carbon is locked into the building fabric, a tangible environmental benefit with every block used.

Excellent thermal and acoustic performance
The combination of insulation and thermal mass helps regulate indoor temperatures, reduce heating and cooling demand, and create quieter, more comfortable spaces.

Summertime Overheating Protection
Protection against Summertime overheating is an often overlooked aspect of insulation, but it is an area where both Hemp blocks and wood fibre excel! Due to the density of the blocks, the indoor temperature is kept at a more consistent level during the hottest parts of the day. The result is a steady internal temperature rather than huge peaks and troughs in line with external temperatures. Now for the technical bit (these numbers are phenomenal in our opinion)

• At 300mm the wall will have a phase shift* of around 16 hours.
• At 240mm the wall will have a phase shift* of around 13 hours.

*Phase shift (or time lag) is the delay between the peak external temperature of a building surface and the peak internal temperature it causes. 

Breathable and healthy indoor environment
Correctly installed Hemp block/wood fibre constructions naturally manage moisture, improving indoor air quality and preventing condensation or mould, all of which are essential for a healthy home or workplace. 

Fire, pest and mould resistant
Hemp blocks are non-flammable, pest resistant and anti-fungal, offering peace of mind without relying on chemical treatments.

Quick and versatile installation
Hemp blocks are lightweight, easy to handle and can be laid with standard tools and methods, meaning no specialist equipment is required. They’re suitable for both new builds and retrofit projects, offering flexibility for different designs and performance targets.

Design flexibility and space gains
Because these blocks now deliver greater performance in a slimmer wall build-up, you can increase internal floor area without compromising thermal or acoustic quality.

 

In summary

With this updated independent testing, hemp block insulation now offers even greater efficiency, cost savings and design freedom than we thought, whilst maintaining the natural, breathable qualities that make it one of the most sustainable building systems available today. 

If you’re designing or specifying a natural or low-carbon building, now is the perfect time to take another look at hemp blocks.