Guidelines for the roof construction including a membrane

Question:Which is the needed distance between the battens for invisible solar power?

Answer: The std. slate roofing battens (typically 35x35 mm) must be spaced 153 mm (plus 3 minus 0 mm), note the under-slate waterproofing vapour diffusive membrane between the rafter and the battens.

Question: How do the roofing company insure a perfect water tight roof?

Answer: use one meter wide under-slate waterproofing (in rools) arranged preferable horizontally with 150 mm overlap and a thick wood strip over the bitumen felt on each rafter / under the battens.

1. Use only advanced under-slate waterproofing vapour diffusive membrane
2. Mount one felt strip at a time and then the battens
3. Secure the one meter wide felt with large headed nails
4. Insure the felt is stretch and the overlap is 150 mm
5. Wood strip for distance under battern and felt 15-20 mm and width as the rafters
6. Insure that NO felt holes, scratches, damages are present - in case of a hole glue a piece of bitumen felt sheet on with bitumen

Question: How is the design of a bullet proof roof including invisible solar panels?

Answer: 1. rafter, 2. under-slate waterproofing, 3. thin impregnated wood list, 3. battens, 4. solar panels, 5. BituSun glue, 6. stone slates - and for the serious people also >100 mm mineral fiber insulation in the roof some 50 mm below the under roofing felt

Question: How does the optimum construction look like?

Answer: Check it out on the photo including under-slate waterproofing

Question:Who can supply this under-slate waterproofing membrane?

Answer: In Europe some 25 manufactures offer such product. In South Africa its available from: Lafarge under roof - Monier Roofing South Africa - www.monier.co.za

Question: What is the weight of the solar panels?

Answer: The total solar panel weight is app 19 kilo per m2 - The roof must be capable of the extra load of 12 kilo/m2 solar panels, plus the fluid weight of 2.5 kg/m2, plus the BituSun glue 5 kg/m2.

Question: Is there a need for gluing the slates onto the aluminium cassettes?

Answer: Yes, absolutely - the solar panel performance will increase, and be maximum when there is no air gap between the stone slates and the aluminium cassettes. And at the same time a minimum amount of BituSun glue is better than over doing it.

So - high accuracy in adding the BituSun glue gives higher solar system performance.

The traditional layers of bitumen felt in between the slates reduce the solar system efficiency.

Question: Is there a need for nailing the slates onto the battens?

Answer: In general a good idea - though depending on:

• Area location, wind load, but -
• Low pitch/angled roof - the BituSun glue is sufficient to insure the slates stay in place - HelioPower do not recommend nailing and take no responcibility for roof tightness if nailed
• High pitch/angled roof - nailing is needed in order to avoid the slates slip of the roof

Question: Can we improve the home comfort via roof insulation? Absolutely - and hereby reduce the needed power for air-condition significantly.

Answer: High cost homes should be insulated with >50 mm in every outer wall and >150 mm in the roof. Which after all is the recommendation from the South African state!