Positive Input Ventilation advice, please

Morning folks,

Our 1970s 4-bed, 2 floor house suffers from condensation on the windows most morning, and has poor air extraction in the kitchen/bathrooms. As such, I am considering getting a Positive Input Ventilation unit installed in our cold loft.

I’m guessing something like this would be appropriate: Drimaster-Eco Positive Input Ventilation System

Has anyone got experience of these? Is PIV the right way to go, or is there a better way of reducing humidity in the house?


I would focus on more targeted extraction. These are not a good idea for several reasons.

Instead go for:

A better cooker hood, fitted closer to the cooking surface.

A humidistat extractor fan in the bathroom. Use window wipers after showers to get water down the drain.

Laundry can be dried in room on the leeward side of the building with the window opened a tad. Or use a heat pump drier.

In the bedroom, leave the vents open overnight to provide fresh air and use thicker duvets. A cooler room with fresh air is better than a warmer damp room with high co2 levels.

Condensation on windows is better that condensation in your walls due to positive pressure gradients forcing humid air onto cold interstitial surfaces. You can see the water on the window, and there will be thermal energy and ventilation available to dry it quickly in the morning, not so much within your wall.


Do you have any trickle vents on windows?
If you have no background ventilation then that may well be the place to start.
You could look at Aereco EHT ot EHT2 inlet vents in (say) a couple of bedrooms and in a living room.
EHT | Aereco
This plus improved bathroom / kitchen extract (as per message from @Frank_Reif) would probably provide a big improvement.


I’m sure I’ve already answered an almost identical question recently but I can’t find the thread or post.

Basically, don’t do it. By forcing the house air into the building structure, where it will cool, you will be dehumidifying the air in the house and saturating it’s structure.

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Which? magazine did a couple of articles on the Drimaster to deal with condensation a couple of years ago but these have proven tricky to retrieve. Not sure they endorse its use now. We use single room heat recovery units sized for the rooms and these work very well n the bathroom and kitchen.

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