During recent hot weather I've noted that the loft space has been reaching temperatures in excess of 50°C. I was wondering if the house would benefit from having a cooler loft space? If so, what might be the optimum way to achieve this?
The house is a 1960's bungalow with the second floor built into the roof. The roof is at a 40° pitch, with approximately 1.5m of loft space above the second floor, and 2m wide lofts to the sides of the second floor. We have cavity wall insulation, a minimum of 300mm of loft insulation on the second floor horizontal ceilings, and 100mm PIR insulation on the small sloped ceilings that follow the roof line. The soffits (effectively at first floor level) are vented, and there is a minimum of 70mm air gap between the roof and any insulation. The insulation and soffits were all installed 7 years ago and we've had no issues with damp or mould since. The roof is original and made of concrete tiles on a felt - the roof is in a very good state considering it's age, although the felt is showing some minor signs of age.
On a windy down there is an obvious draft in any of the loft spaces. For the air to circulate it needs to enter the vented soffit at once side of the house, raise up an over the second floor rooms and back down the other side and out. Generally this seems to work well. However on recent hot days there has been next to no wind, and thus next to no air movement in the loft. As the soffits are a good 3-4m below the apex of the roof and hot air rises, the hot air seems to get trapped in the roof during an evening. Some cooling does occur throughout the night but not enough to bring the loft space down to match outside air temperature.
I'm trying to work out if there would be a summer time cooling benefit to the house by ventilating the loft? Possibly by using vented ridge tiles or air bricks. Or would the insulation already in place mitigate any of the heating effects caused by the body of hot air in the loft? Thus making any expenditure on further venting the loft unbeneficial. Is venting the loft further likely to have a notable negative impact on keeping the house warm during the winter months?
I don't think this question has been covered before on the forum (or, possibly my searching skills are poor), apologies if it has and thank-you for any insights anyone can provide.
The house is a 1960's bungalow with the second floor built into the roof. The roof is at a 40° pitch, with approximately 1.5m of loft space above the second floor, and 2m wide lofts to the sides of the second floor. We have cavity wall insulation, a minimum of 300mm of loft insulation on the second floor horizontal ceilings, and 100mm PIR insulation on the small sloped ceilings that follow the roof line. The soffits (effectively at first floor level) are vented, and there is a minimum of 70mm air gap between the roof and any insulation. The insulation and soffits were all installed 7 years ago and we've had no issues with damp or mould since. The roof is original and made of concrete tiles on a felt - the roof is in a very good state considering it's age, although the felt is showing some minor signs of age.
On a windy down there is an obvious draft in any of the loft spaces. For the air to circulate it needs to enter the vented soffit at once side of the house, raise up an over the second floor rooms and back down the other side and out. Generally this seems to work well. However on recent hot days there has been next to no wind, and thus next to no air movement in the loft. As the soffits are a good 3-4m below the apex of the roof and hot air rises, the hot air seems to get trapped in the roof during an evening. Some cooling does occur throughout the night but not enough to bring the loft space down to match outside air temperature.
I'm trying to work out if there would be a summer time cooling benefit to the house by ventilating the loft? Possibly by using vented ridge tiles or air bricks. Or would the insulation already in place mitigate any of the heating effects caused by the body of hot air in the loft? Thus making any expenditure on further venting the loft unbeneficial. Is venting the loft further likely to have a notable negative impact on keeping the house warm during the winter months?
I don't think this question has been covered before on the forum (or, possibly my searching skills are poor), apologies if it has and thank-you for any insights anyone can provide.
