Are thermal calculations done in the same way for all building elements?
Generally speaking, yes - all calculations are done by the 'combined method'. However, ground floors differ slightly from other building elements in the information that is required. If requesting a calculation for a ground floor, please ensure that you provide a floor area and length of the exposed perimeter (i.e. the length of new floor along outside-facing walls). This allows us to calculate a perimeter/area ratio, which is crucial in the floor calculation.
Can a breather membrane be laid directly over Recticel's insulation boards?
Different breather membrane manufacturers have different guidelines for their products, and these should always be consulted prior to installation. It may be possible to lay the breather membrane on the insulation, but with a counter batten airspace above.
If you would like to discuss application of any specific project, please contact our Technical Services.
Can electric cables be channelled into Recticel insulation boards?
No, as this would reduce the performance of the boards. Cables can penetrate the insulation with no detriment to the cable sheathing. Any cables penetrating or lying against insulation should be oversized to cater for increased operating temperature. If in doubt, consult a qualified electrician.
Can I get a U-value calculated for my project using Recticel Insulation products?
Absolutely! Please contact our freephone technical helpline on 0800 085 4079 or use our free of charge U-value calculator here.
Can I recess cables into Recticel PIR insulation boards?
Cables should not be recessed into the insulation boards. They may be laid between two layers of boards with the cabling oversized to accommodate for an increase in operating temperature. If cables penetrate an insulation layer, PIR will have no detrimental effect on cable sheathing.
Further guidance on the above should be obtained from a qualified electrician.
Can I recess downlighters into Recticel PIR insulation boards?
General best practice in such scenarios would be to include for a battened service zone to avoid compromising the performance both the insulation and the vapour control layer. The required depth of this “void” should be determined by the requirements of the specific lighting manufacturer.
If this is not suitable and the lighting needs to be recessed, then advice should be sought from the downlighter manufacturer.
For more information regarding this, an information document can be found within the IMA Resource Centre on the 'Use of downlighters, recessed lights or spotlights and PIR PUR insulation' here.
Can insulation be placed between and over flat roof joists?
BS 5250:2011, the British Standard for the control of condensation in buildings, does not recommend installing insulation between timber joists as well as above the deck.
However, not all hybrid roofs will show condensation risk, our Technical Services team will be happy to assist with U-value calculations and condensation risk analysis where required, we will also discuss the potential risks involved, but please note all calculations will be marked “NOT RECOMMENDED” inline with the British Standard.
Do I have to follow a training course regarding the safe use of diisocyanates?
How thick do I need to insulate?
We recommend that you seek advice from your architect, designer, energy assessor etc. to determine the appropriate insulation thickness. If you already know the desired performance, you can contact our Technical Services team for U-value calculations or look up the required R-value and corresponding thickness in the technical datasheet.
The cleanest energy for heating and cooling, is the energy you do not have to use. That is why we recommend to insulate a flat roof to a higher standard than the minimum requirement. We recommend a minimum of 45 mm Deck-VQ® (Lambda (λ) = 0,009 W/mK) for renovation and 60 mm (Lambda (λ) = 0,008 W/mK) for new build.
Speak with our technical experts
What air gap is required between insulation and breather membrane?
This should be confirmed in the membrane manufacturer's BBA certificate, though 25mm to 50mm is typical.