Insulating attic spaces to keep your house inherently cool

Roofs are often the cause of reduced thermal efficiency in summer and winter. Insulating attic spaces is first thing to do when you renovate. Your energy bills plummet immediately when you remove the need for air conditioning in summer.

We discussed the subject with Dominique Burg, a specialist in eco-friendly materials for renovations working from an office in the Quercy area in south-west France. The environmentally preserved Quercy area has naturally led him to opt for hempcrete solutions, to stay in keeping with his clients’ preferences.

He also works on new builds. The house he is currently building is ideal for testing different casting methods to increase his efficiency on projects involving this material in the future.

• 1/2 Entreprise SEE Burg
• Interview with Dominique Burg on 14 May 2018: Weber Tradical®

Weber: Why is a well-insulated attic so important for you?

Dominique Burg: We get a lot of sunshine in our region, with average temperatures of around 30°C in summer. To keep indoor spaces cool, I’m a strong advocate of installing insulation that’s effective for that period of the year and can counter overheating.

Having an attic you can use as a pleasant living space is a real plus for house owners. My approach is therefore to offer an environmentally friendly solution that cuts back on energy costs.

Hempcrete has proved to be the ideal solution for insulating attic spaces under these conditions.

Weber: Have you ever tried other solutions? On earlier projects for example?

DB: Yes, I have actually tried using lightweight insulating materials such as cellulose, wool and so on, but they don’t work in summer. If you don’t have air conditioning, converted attic spaces just can’t be used. And let’s not forget that air conditioning is not only high-maintenance but also uses a lot of electricity.

It’s absurd to have an energy bill that’s larger in summer than in winter. The real issue is how to keep the temperature down indoors. What people want in a home is a good living atmosphere.

Hempcrete is as effective in summer as in winter.

Weber: How are you organised in terms of casting?

DB: We made the most of this building project to try out the different ways of casting hempcrete, the main aim being to gain in efficiency on projects in general. We compared the times for casting hempcrete using a mechanical projection solution and a solution involving a mobile concrete mixing station with a telescopic chute.

Weber: What were the main differences between these two processes?

DB: We had to install the equipment for mechanical projection quite high up to reduce the length of the pipe and ensure it was level as much as possible. This was to obtain the maximum possible output of 3 m3 per hour.

As for the mobile concrete mixing station, the procedure was completely different as we were mixing large quantities of hempcrete – up to 40 m3 per hour. The Tradical® lime + Chanvribat ® hemp + water mix was very high quality. The real output was actually dictated by the speed at which the hempcrete could be cast for the roof.

Weber: What did you do in terms of lost formwork?

DB: Here again I made the most of it to try out two very different solutions. In the first case, the lost formwork consisted of storey-height panels. The advantage is that you can apply the finish directly on these substrates. In the second case, I used battens made of poplar. This is a stronger substrate and also has the benefit that you can dissociate the finish from the lost formwork and thus the hempcrete.

Weber: What else is on the programme for the rest of the house?

DB: We’re going to compare the same two casting methods for creating 120 m² of insulated walls and insulating Tradical® hempcrete screeds. We’re also going to apply a lime and sand render to finish the exterior of the house. The interior is going to be decorated using a mix of moisture and heat-regulating hemp renders and lime plus mud renders. Heating will be provided by a masonry stove.

The house will soon be ready to show off its energy efficiency over the summer and throughout the following seasons!

Project profile

• Project owner and main contractor: Dominique Burg
• Town: Saillagol, France
• Surface area: 160 m2
• Altitude: 300 m
• Climate zone: H2c
• Insulation: The roof, wall and screed are cast with Tradical®Hempcrete
  • Using Tradical®Thermo + Chanvribat®
    • An approved material blend that complies with the performance requirements laid down by French professional rules.
    • Certified fire-resistance rating
    • Certified lambda value of 0.056 W/m.k for attic insulation and 0.076 W/m.k for wall insulation.

For further information

• Entreprise SEE Burg – Saillagol (dpt 82) – France – www.burg-construction.com
• Tradical® Contact: contact@weber-tradical.com