Tommy8884

Thanks both. I was referring to the to house and from house side of the ducting. I think as it's only a very short run I will leave the from outside duct, but the point around overheating is well made and I hadn't considered that. Thanks

Hi All, I have finally got around to installing my MVHR. Its in a VERY tight unheated loft. I have built an insulated box for the system itself (a box lined with some spare multi layer foil insulation). I'm in the process of looking for ducting options, its going to be challenging as the loft is so tight (very low pitched roof) Anyway, all advice seems to say insulate the supply and exhaust. I'm struggling to understand why I would in my case, with the loft space being unheated, the temps should be close to outside in winter, so there is certainly no point insulating the supply, and probably not the exhaust? The exhaust might be a contender but will only have about 1.5m to run to the outside. I of course intend to insulate the supply and exhaust to the house. Mostly by placing between the 2x150mm layers of insulation in the loft. Thanks in advance

Thanks for the reply. So I will use a plenum system for the to/from house vent points back to a manifold. I need 150mm duct to/from house and to the manifolds. Would the above duct work for that? Seems to be semi flexible but relatively smooth inside. Thanks again

Hi. I'm a newbie to this. Just purchased a custom made MVHR and will be fitting in the loft. The unit is fitted with 150mm spigots for all 4 ports. I want to use as little flexible ducting as possible. I've found some cheap twin wall pipe (probably drainage). Looks very similar to the semi rigid MVHR stuff you get in 75mm but 150mm. See attached pic Is there any reason why j can't use this if I insulate it (will be in a loft). Or, am I missing something