PIV system questions

ChasingtheWelshdream

Just mooting ideas at the moment and have read good things about PIV systems.

Does their effectiveness depend on the house layout and lifestyle?

We are three storeys, so would the loft system have any impact on the ground floor?

I understand there is a single ‘vent’, usually on the landing ceiling. I presume there will be no benefit to bedrooms unless the doors are left open? 

rob7475

The effectiveness will depend on the layout to a certain degree. It should still work on a three storey house though. You'll probably find that the worst of your condensation problems are on the upper floors anyway in bedrooms and bathrooms.

A single vent is usually placed on the landing and as long as doors are left slightly ajar, it will work fine. Even closed doors don't usually cause an issue as there is usually a gap at the bottom of the door.

Your other option is MHVR but I think retrofitting is more complex as you need ducting to each level of the house.

ChasingtheWelshdream

Thank you, I hadn’t thought of the gap at the bottom of the doors. Bedroom doors are mostly shut so that is good to know.

Ducting wouldn’t be practical for us for MHVR.

We actually have two lofts. The main part of the house is 3 storey, with a 2 storey section at the back with one central stairwell. Would it be beneficial to have a PIV in each loft or just the main one?

rob7475

I'd go with just the one to start with and see how you get on. I've installed the Nuaire drimaster in my house and I'm very happy with it. Nuaire have a good customer service team - it might be worth having a chat with them to see what they recommend.

ChasingtheWelshdream

Thank you, very helpful.

Apjs87

PIV units do really help in eliminating condensation but be aware you will notice a temperature drop in the area/rooms around where the vent is installed.

1616six

I’m keeping an eye on this thread as we are due to complete on a house in December which has a PIV system but I know nothing about them, just read it in the advert!

rob7475

SPnomore said:

Basically, you are paying to make your house 'leaky'. So people seal up their homes to keep the heat in, pay money to warm it up, then install a fan in the loft to force the heated air out wherever it can escape under pressure.

You're kind of right. However, PIV units tend to be pusing moist air out of the house and replace it with "drier" air. The less moisture in the air, the quicker it is to heat up.

I've not noticed an increase in heating usage since installing PIV around 5 years ago.

MHVR is a better solution but for many it's not a suitable retrofit option. Dehumidifiers are also an option but generally cost much more to run.

ChasingtheWelshdream

Our house was originally designed to be leaky, but modern ‘improvements’ have sealed up the areas that would have provided this ventilation and breathability  (eg installing draught proof windows without trickle vents, removing lime plaster.)

So PIV could be a way to address this imbalance, and seems a cost effective, controllable option rather than opening windows/running dehumidifiers. I’m thinking anyway

FreeBear

rob7475 said: MHVR is a better solution but for many it's not a suitable retrofit option.

I have looked at installing a MHRV system here (3 bed semi). The cost is the key thing putting me off at the moment. In the meantime, I may well install a PIV system to pump a small amount of air into the landing/stairwell.

markin

A piv is a last resort after fitting bathroom/kitchen extractors, And a dehumidifier must be far cheaper to run being that every watt of heat generated stays in the house,  certainly for electric heated homes.