Ventilation Duct Manifold 1 to 3 Home Made

By Andy the stuff doer

This is probable the first mention of the MHRV (Mechanical Heat Recovery Ventilation) so here’s a quick run-down of the thinking behind it.

The Cottage will be a  holiday let,  if it was just us I probably wouldn’t  have gone to the time and expense of installing the system, we would open windows and turn on fans when necessary.   Old buildings such as this one can suffer badly from damp rusulting from our modern ways living. Holiday makers won’t necessarily treat the place like we would.  So as the technology is available and now tried and tested, I’m prepared to give it a go. 

The system draws warm moist air from the kitchen and bathroom and transfers the heat to fresh air that is ducted through in to the bedrooms.  The unit runs at a low speed constantly supplying a flow of clean fresh air through the whole building. It will turn to full power when moisture from cooking and showering or even clothes drying is detected.

I’ll go in to more details at a later stage but for now it means I have to install the ducting in as discreet a way as possible.  I’m also minimising the potential noise, it’ll have to be virtually silent so it doesn’t bother anyone and I don’t want cross talk from room to room via the ducting.

Ventilation ducting behind attic dwarf wall

Ducting fitted where it wont be seen. Difficult in an old property.

Being such an old house without the normal spaces to run ducting the design is fairly challenging.  This post covers a quick look at the manifold duct splitter and silencer I had to make and install before fitting the dwarf wall in one of the attic rooms.

Ducting manifold splitter to flexible ducting from ridged duct

The Splitter manifold with the three flexible ducts fitted

The inlet is 60 x 220mm rectangular ducting that will be fitted above a false ceiling in the bathroom  it then splits to three outlets to 4 inch insulated flexible ducting  running to each of the attic bedrooms and to the living room.  The flow rates in the flexible ducting will be low enough not to cause noisy turbulence.  The flexible duct is sound absorbing and as they don’t connect directly together like with tee joints the cross talk is reduced.  The manifold box has sound absorbing insulation on the inside wall to further attenuate any noise.  No way could I find a suitable commercial product to do all this in the space available.

three way duct manifold custom made

The ventilation duct manifold showing the rectangular inlet and the 3 x 4" inch outlets

Construction is simple and the materials cheap. I used sections of plastic ducting, these are easy to cut with a jigsaw and to shape using a heat gun.  The joints are welded with plastic solvent screwed and sealed with a building adhesive (I think it’s called “stick like s**t”, I’m sure other brand are available).

home made duct manifold internal details

Belt and braces approach to the construction. It will last !

If you fancy making your own, these couple of pictures might give you some ideas, If you want to know more drop a comment on below and I’ll see what I can do.

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