The Celotex Pitched Roof Technical Twitter Takeover
The February Technical Twitter Takeover saw focus on pitched roof application, including topics such as Building Regulations, ventilation and insulation between rafters.
Let’s crack on with the questions.
Question 1 – What U-values do I need to achieve to hit Building Regulations for an existing pitched roof? #AskCelotex. Under normal circumstances, existing pitched roofs would require a u-value of 0.18 W/m2K.
Question 2 – Do my rafters need to be ventilated? Below sarking felt a minimum of 50mm ventilation is required. Below a breather membrane a drape space is required, but no ventilation.
Question 3 – Can I ventilate below the insulation? #AskCelotex. Any construction layer to the outside of a ventilated cavity will receive no value as regards a u-value calculation.
Question 4 – Does Celotex have a BBA Certificate for pitched roofs? Yes. Our BBA Certificate offers advice and guidance on the correct use of Celotex within pitched roof applications #AskCelotex
Question 5 – Should I insulate at pitch and ceiling level? To contribute towards your insulation envelope you can insulate at either pitch or ceiling level but wouldn’t usually insulate at both.
Question 6 – Can I insulate to the outside of my rafters? #AskCelotex. When incorporating a breather membrane and counter batten, insulation can be positioned between and over rafters. The layer to the outside should be equal to or greater than the layer between, in order to guard against harmful condensation.
Question 7 – Do I need a vapour control layer, even though I have a breather membrane to the outside of the insulation? A VCL should be positioned to the warm side of all insulation in order to minimise the risk of harmful condensation.
Question 8 – How do I fit Celotex between rafters? #AskCelotex. Celotex should be cut with a fine tooth saw to fit tightly between rafters. See the pitched roof specification guide for full installation guidelines.
Question 9 – What size are the Celotex boards? The standard Celotex board size is 1200mm x 2400mm
Question 10 – What Celotex insulation boards are suitable for positioning under the rafters? Celotex GD5000 with joints sealed in line with standard plasterboard practices and FR5000 with joints taped using a foil backed tape are ideal for underdrawing rafters and creating a VCL without the need for an additional membrane.
A good takeover for those considering a loft conversion, answering some common questions on all types of aspects that relate to pitched roof application. If you would like more information regarding Celotex in a pitched roof application, visit the website for product and installation recommendations – Celotex Pitched Roof