Cellulose wadding used as insulation for lost roof spaces: why this solution?
This winter we have improved the insulation of our attics lost thanks to bulk cellulose wadding.
Obviously we wanted to use a natural insulation, this dossier aims to present this approach and to answer the question: why and how have we improved the insulation of our roof spaces with loose cellulose? Here are some answers.
Why cellulose wadding?
La cellulose wadding We believed to be the best compromise of economic insulation for the following reasons:
- Excellent insulating properties
- Quite easily applicable by itself for lost roof spaces
- Moderate and very low price compared to other natural insulators
- Good behavior in time
- Very good summer comfort (much higher thermal capacity than synthetic wool)
- It is a revalued waste
- Easy to buy *
* Indeed, currently in 2008, it is still very difficult to find certain other natural insulators delivered to your home (at an attractive price ie not 10 times the price of chemical insulators) although I regret a little that our cellulose comes from Austria but currently, this country seems to hold the European monopoly of the manufacture of cellulose insulation.
The straw would have been an even more ecological insulator because its impact is zero but we have ruled out this solution because its implementation is more delicate and especially finding it locally is almost impossible (it is obviously not produced industrially).
This choice of cellulose was not instantaneous since a fairly long reflection was carried out on our forums.
Thus, for all those interested in the subject for their project, you can read the subject natural insulation for lost roofs where many questions / answers are asked.
What thickness of wadding?
We wanted a thermal resistance R equivalent to the 2005 Thermal Regulation RT2005 is R = 6 to 6,5.
With a lambda of 0.04, we will therefore need to lay approximately 25cm thick of loose cellulose.
What price per m²? The natural, ecological, cheaper than the chemical!
We had to isolate 44 m² including an access hatch where it was obviously impossible to put loose cellulose. So we opted for a few m² of hemp wool panels and we made a small "formwork" as indicated on the page: bulk insulation, the preparation of the attic.
So here are the details of the bill for our insulation:
- 30 bags of 370L: 428.40 € is 11.1m3 or 38.59 € the m3
- 3 hemp wool panels 20 cm: 72.43 € for 2,07 m² is 174.15 € the m3
- Shipping and delivery: 86 €
TOTAL PRICE: 586.83 for 44 m ² approximately is 13.37 € the m² in R of 6,5!
A few comments:
- This cost is the delivered price but not posed (pose by ourselves)
- This price per m² is very reasonable, so contrary to what one might think insulating "green" with cellulose is not expensive, quite the contrary!
- By taking 100% cellulose we would have had a cost of 10.20 € / m² for an 6,5 R
- Taking 100% of hemp panels against us had a cost of 35.00 € / m² for an 5 R. There we can talk about "ecological luxury", so we used a minimum of hemp!
- A bonus / subsidy (not specific to the installation of natural insulation) can also be allocated to you. In our case, this Walloon Region premium amounts to around € 160, which is far from negligible.
- The delivery (not negotiable unfortunately) is a significant extra cost of 15%
- Bulk rock wool is more expensive than cellulose, see image (LM catalog) below: with equivalent thermal resistance, we get more than 20 € / m² for loose rock wool!