Don’t Install Solar Until You Fix Your Roof, by Passive House Technology on YouTube. 10 min 30 s.
- Video length
- 10 min 30 s
- Time to do it
- 1 to 2 days
- Difficulty
- Medium
- Steps
- 9
What you need
Steps
Check the roof covering and loft for damaged tiles, damp patches or sagging. Repair leaks and rotten timber before you add any insulation or plan solar panels.
Measure the depth of insulation already in the loft. Top it up to at least 270 mm with rolls or boards laid between and across the joists.
Seal air leaks where warm air escapes: gaps around pipes, cables, loft hatches and downlights. Use sealant or draught-proofing tape.
Keep a clear gap at the eaves so air can flow under the roof. Fit eaves guards or vent trays if insulation blocks the airflow.
Lay a vapour barrier or use foil-backed boards on the warm side where the build-up needs one. Tape the joints so moist air cannot pass through.
Deal with thermal bridges at wall plates, chimney breasts and loft hatch edges. Insulate these joints continuously so cold spots do not form.
Check ventilation in the loft and roof space. Make sure vents are open and not covered by insulation, so moisture can escape in winter.
Plan summer shading before solar: note roof direction, nearby trees and how much sun hits the roof. Shade reduces both heat gain and panel output.
Only after the roof is sound, insulated and ventilated, get quotes for solar panels sized to your reduced energy use.
Tips and common mistakes
Never cover downlights or recessed fittings with insulation unless they are rated for it, as they can overheat.
Wear a dust mask and gloves when handling old insulation, which may contain irritants.
Do not block eaves ventilation, as trapped moisture can rot roof timbers.
Fix roof leaks before installing panels, since removing panels later to repair a roof is costly.
Questions
Can I install solar panels on an uninsulated roof?
You can, but it wastes the chance to cut energy demand first. Insulate and seal the roof, then size the solar system to your lower energy use.
How much loft insulation do I need?
Aim for at least 270 mm of insulation. Top up existing layers and keep the eaves vents clear so air can still flow.
Why does roof ventilation matter in winter?
Ventilation lets moist air escape so it does not condense on cold roof timbers. Blocked vents can lead to damp and rot.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
