Insulation boards in truss loft

[andyste]

Our house (built around 2000) has a hip roof. Most of the loft is filled with trusses but the central area has a series of inverted 'V' joists going up to the top of the roof, creating an open area approx 8'x8'. I was considering turning this into a small, occasional use room (office/man cave) but I'm concerned about the temperature extremes - single figures in winter to well over 30 in summer.

Put insulation board on the entire roof would be an expensive job and I would struggle to do it all due to the limited access in some areas. I was wondering instead about boarding just this central 'V' area, and up the trusses at either end, effectively making a tent-shaped room.

I was wondering how effective it would be in regulating the temperature, or would I just be introducing other issues? I can imagine such a small space getting very stuffy.

I was also thinking of boarding the central part of the roof (front and back), and boarding up the last truss at either end, so again creating a "room" within the loft. It would be a bigger area, so less likely to get stuffy, but still unsure how much it would help with the temperature?

A heater and velux would obviously help greatly, but the latter is outside of my budget at the moment.

 

[Bonni]

Only put insulation between the rafters under the tiles only if the room will be heated and ventilated otherwise you will suffer condensation.

Converting a loft is the most costly extension and it puts the least value on the house. Even partially converting the loft will still be costly and I wouldn't like to be sat in there often with no fire escape (appropriate Velux at the correct height).