Installing a PIV system, which unit and should we have a radiator in the landing?

ashe

I'm thinking to get a PIV system installed to help with air circulation in the house and cut down on condensation. 

One thing I'm wondering is I've read that the air can be a little colder due to bringing in fresh air via loft, so heating may cost a little more. 

Trouble is we have a very small radiator in our hallway, and no radiator on the landing, so concerned this will make both these rooms colder. We've got about the largest radiator we can fit in the hall, we could put one in the landing though but not sure if this is seen as a waste of time - is there normally one there?

for PIV systems have seen some with heaters but these look to be 500w or so so would be very expensive to run long term 

I was thinking of this one?

https://www.i-sells.co.uk/mob/prod_detail.php?products_id=45546&ref=var

Ben1989

We have the exact same one but with a carbon filter.

It obviously does bring in fresh (cold) air which you can feel but it's not a huge amount at all. There are different speeds so the top speed is more for a 5-bedroom detached house and the lowest speed for a bungalow.

From my research before getting one people mentioned that it's a waste of time getting the heating element as it hardly warms the air up and you're adding more electrical expense for not a proportional benefit.

1616six

Ours looks very similar, it was already fitted when we moved in but from looking in the loft, it’s certainly that style. 

If you put your hand near the ceiling vent it’s certainly cool air that comes in but to be honest I’ve not noticed much difference to any other house we’ve lived in. Certainly not to the extent I’d change rads.

Doozergirl

I can't helping thinking that a standalone MHRV might be a better answer than PIV with a heater, given that it doesn't heat anything but recycles the warm air it already takes from the house. 

 

theonlywayisup

MVHR (or whatever order you chose to have the abbreviations!) all the way.  As Doozer says it doesn't heat anything but draws the heat from the warm air. 

ashe

theonlywayisup said:

MVHR (or whatever order you chose to have the abbreviations!) all the way.  As Doozer says it doesn't heat anything but draws the heat from the warm air. 

What is the cost though? I had a quick Google and it was suggesting about £1500 for an mhvr/whatever system and said you need to duct to every room that will have it? Our loft is already a bit of a spaghetti junction so this might add a lot of cost and complexity to the install 

rob7475

MVHR is a good option in a new build or renovation project. Retrofitting isn't so simple though. PIV isn't as good as MVHR but as a retrofit option it works well. We have had it in our house for about 5 years and although the landing is a little cooler, it's not a problem. We did buy the Nuaire unit with the heater but I leave the heater off as it never made any noticable difference to the air flow temperature.

ashe

Yeah I think if ducting was easy and money no object I'd definitively go down that route 

tacpot12

The 500w heater shouldn't cost that much to run as it should have a thermostat so that it only operates when the incoming air is much lower than the indoor temperature. If it is adjustable, I would have it set to 7C. 

You won't feel a lot of benefit from the heater if you put your hand into the airflow; it will still feel 'cold', but the heating system will notice the additional 0.5kW of heat being put into the house and it will stop the heating system from struggling. If it is struggling now, pumping cold air from outside (even at the relatively modest volumes that a PIV moves when not on boost) will make it worse. If you make sure the heater can be turned off, or adjusted, you will be always be able to manage the extra energy it draws. 

rob7475

tacpot12 said:

The 500w heater shouldn't cost that much to run as it should have a thermostat so that it only operates when the incoming air is much lower than the indoor temperature. If it is adjustable, I would have it set to 7C. 

You won't feel a lot of benefit from the heater if you put your hand into the airflow; it will still feel 'cold', but the heating system will notice the additional 0.5kW of heat being put into the house and it will stop the heating system from struggling. If it is struggling now, pumping cold air from outside (even at the relatively modest volumes that a PIV moves when not on boost) will make it worse. If you make sure the heater can be turned off, or adjusted, you will be always be able to manage the extra energy it draws. 

Most loft spaces stay cold though if they are well insulated so throughout winter, the heater would be running nearly constantly. I have a smart meter now so I might put the heater back on again so I can see how much it uses. I reckon it will be significantly more than the extra cost of running the boiler for a bit longer though.

ashe

rob7475 said:

tacpot12 said:

The 500w heater shouldn't cost that much to run as it should have a thermostat so that it only operates when the incoming air is much lower than the indoor temperature. If it is adjustable, I would have it set to 7C. 

You won't feel a lot of benefit from the heater if you put your hand into the airflow; it will still feel 'cold', but the heating system will notice the additional 0.5kW of heat being put into the house and it will stop the heating system from struggling. If it is struggling now, pumping cold air from outside (even at the relatively modest volumes that a PIV moves when not on boost) will make it worse. If you make sure the heater can be turned off, or adjusted, you will be always be able to manage the extra energy it draws. 

Most loft spaces stay cold though if they are well insulated so throughout winter, the heater would be running nearly constantly. I have a smart meter now so I might put the heater back on again so I can see how much it uses. I reckon it will be significantly more than the extra cost of running the boiler for a bit longer though.

If it's 500w, that's about £4 a day if it runs constantly isn't it? Like you say imagine that most lofts will be freezing right now. Surely that 0.5kw is then heating the much colder air from outside, as opposed to the heating system working on already heated water to warm up
warmer air?