Correct install of thermawrap (aluminium bubble wrap)?

[Robbiebob]

Help, I'm confused - still struggling with an old issue:

I want to put thermal bubble wrap at the rafter level of the loft. At present it is a cold loft (with joist level insulation) but after severe flood damage, I want to make it a warmer loft to prevent pipe freeze.

I have boards covering the joist insulation over most of the loft and have been thinking to bring the bubble insulation on the rafters right down to pin it to the loft boards (adding new boards where necessary).

The intention is during colder spells to leave the loft door open and kind of heat the space.

However I have been told by friends that I must leave a gap for ventilation to avoid condensation. If I do leave a gap I'll have trouble keeping it warm.

If I don't insulate and leave the loft door open, won't I get condensation anyway?

 

[mointainwalker]

If I don't insulate and leave the loft door open, won't I get condensation anyway

?

No, because the warmth coming up will be dramatically diluted by the eaves ventilation.

This is also why leaving the loft-hatch ajar is unlikely to help you in your quest for non-freezing tanks.