Summer comfort: 13 mm of R'BULL brings the temperature down by 25 °C

The summer problem is not the winter one

In winter, heat leaves slowly from inside towards outside. In summer it arrives fast and as solar radiation concentrated on the roof covering. These are not the same mechanisms, and they do not call for the same answer.

What happens under a roof in the sun

The covering absorbs the radiation, heats up strongly and radiates in turn towards the inside of the loft. It is that second radiation, not conduction, which warms the rooms under the slope at the end of the day.

The part played by a reflective face

A low emissivity surface facing a void sends a significant share of that radiation back instead of absorbing it. It therefore acts precisely on the dominant mechanism in hot weather.

How to read a temperature difference

Any measurement of this kind depends on the conditions: orientation, colour of the covering, loft ventilation, time of day. A measured value describes a precise situation, and it is read with its protocol rather than on its own.

What that changes for the occupant

A room under the slope that stays usable in the evening. That is the only measure that really counts, and it is settled not by the room thermometer but by the temperature of the surfaces above the beds.

What remains necessary alongside

Night ventilation and protection of the glazing. No insulation makes up for a south facing window with no shading, and commercial honesty means dealing with all three points together. Ceiling insulation settles the share coming from above, blinds settle the share coming through the glass, and ventilation removes what is left.

Behaviour under roofs is developed on the dedicated page, and emissivity on the emissivity page.