Can you solve this mystery?

Petriix

digannio said:

It's just not true to say that it's like leaving a window open 24/7. I don't know if you've lived with a PIV but within six months I've gone from living without one (lots of condensation everwhere even with bathroom and kitchen doors closed) to living with one (virtually nil condensation most of the time). I know which I would choose. And it's just not true to say you need to keep the heating on because of it. Now I've turned the heater off my leccy costs have normalised.

I don't have an axe to grind, just telling it as it is for me with real life experience of  a PIV. There is hardly any condensation, less dust in the house, the air is fresher (without it being cold) and any smells, like cooking, disperse very quickly.

Your misunderstanding me. Of course the benefits of the PIV system are better than just leaving a window open. But your heating costs will increase as a result - that's an objective fact because you're literally pumping cold air into your house which will require energy to heat. Now that you've turned off the inbuilt heater, your (presumably gas powered) central heating will be picking up the additional demand. Either that or you're living in a colder house.

QrizB

Petriix said:

digannio said:

It's just not true to say that it's like leaving a window open 24/7. I don't know if you've lived with a PIV but within six months I've gone from living without one (lots of condensation everwhere even with bathroom and kitchen doors closed) to living with one (virtually nil condensation most of the time). I know which I would choose. And it's just not true to say you need to keep the heating on because of it. Now I've turned the heater off my leccy costs have normalised.

I don't have an axe to grind, just telling it as it is for me with real life experience of  a PIV. There is hardly any condensation, less dust in the house, the air is fresher (without it being cold) and any smells, like cooking, disperse very quickly.

Your misunderstanding me. Of course the benefits of the PIV system are better than just leaving a window open. But your heating costs will increase as a result - that's an objective fact because you're literally pumping cold air into your house which will require energy to heat. Now that you've turned off the inbuilt heater, your (presumably gas powered) central heating will be picking up the additional demand. Either that or you're living in a colder house.

... but gas heating is currently 1/5th the price of electric heating, so it's still a gain (or at least, a reduced loss) by turning it off.

OP I can see the attraction of PIV and if I had a condensation problem I'd consider something similar. Fortunately I don't!

digannio

Petriix said:

digannio said:

It's just not true to say that it's like leaving a window open 24/7. I don't know if you've lived with a PIV but within six months I've gone from living without one (lots of condensation everwhere even with bathroom and kitchen doors closed) to living with one (virtually nil condensation most of the time). I know which I would choose. And it's just not true to say you need to keep the heating on because of it. Now I've turned the heater off my leccy costs have normalised.

I don't have an axe to grind, just telling it as it is for me with real life experience of  a PIV. There is hardly any condensation, less dust in the house, the air is fresher (without it being cold) and any smells, like cooking, disperse very quickly.

Your misunderstanding me. Of course the benefits of the PIV system are better than just leaving a window open. But your heating costs will increase as a result - that's an objective fact because you're literally pumping cold air into your house which will require energy to heat. Now that you've turned off the inbuilt heater, your (presumably gas powered) central heating will be picking up the additional demand. Either that or you're living in a colder house.

If the PIV has been properly installed and set up correctly and in the correct place in your home then it shouldn't have a significant impact on your heating. Do we now have to keep the heating on longer? No. Does the heating take a lot longer to reach goal temperature? No. Does the house generally feel cold? No. It would be wrong to suggest that there is a cold blast of air fighting against the room thermostat. The effect of the ventilation with a PIV is more subtle and gentle than the impression you are giving. But maybe you haven't lived with a good one, I don't know.

Spies

Surely it depends on the house, we struggle to heat our home to a satisfactory level without a PIV, with a PIV it may never hit the target temperature. 

Petriix

digannio said:

Petriix said:

digannio said:

It's just not true to say that it's like leaving a window open 24/7. I don't know if you've lived with a PIV but within six months I've gone from living without one (lots of condensation everwhere even with bathroom and kitchen doors closed) to living with one (virtually nil condensation most of the time). I know which I would choose. And it's just not true to say you need to keep the heating on because of it. Now I've turned the heater off my leccy costs have normalised.

I don't have an axe to grind, just telling it as it is for me with real life experience of  a PIV. There is hardly any condensation, less dust in the house, the air is fresher (without it being cold) and any smells, like cooking, disperse very quickly.

Your misunderstanding me. Of course the benefits of the PIV system are better than just leaving a window open. But your heating costs will increase as a result - that's an objective fact because you're literally pumping cold air into your house which will require energy to heat. Now that you've turned off the inbuilt heater, your (presumably gas powered) central heating will be picking up the additional demand. Either that or you're living in a colder house.

If the PIV has been properly installed and set up correctly and in the correct place in your home then it shouldn't have a significant impact on your heating. Do we now have to keep the heating on longer? No. Does the heating take a lot longer to reach goal temperature? No. Does the house generally feel cold? No. It would be wrong to suggest that there is a cold blast of air fighting against the room thermostat. The effect of the ventilation with a PIV is more subtle and gentle than the impression you are giving. But maybe you haven't lived with a good one, I don't know.

It's impossible to quantify your anecdotal observations about how long the heating is running for; there are too many variables. I've used significantly more gas in the past 12 months than in the preceding year simply because temperatures have been lower. 10% extra demand could easily be hidden in the variations. 

If you know the flow rate of the PIV system and the average temperature differential between the loft and the house then you could calculate it. Back of an envelope estimate would be ~ 1kWh every 3 hours the system is running for the coldest 4 months of the year. That's ~ 1000kWh additional demand on your heating. Not enormous, but definitely not insignificant.

If you disagree then please share your calculations. 

digannio

I don't have calculations but I know that my bills are normal. The heating gets up to goal temperature quickly and I don't have to have it on for excessively long periods of time. That's my practical, real experience. Can you tell me what kind of PIV you had in your house, where it was, how it was set up and what settings were used etc. Because your real-life experience of one in a home setting is important. 

QrizB

Petriix said:

If you know the flow rate of the PIV system and the average temperature differential between the loft and the house then you could calculate it. Back of an envelope estimate would be ~ 1kWh every 3 hours the system is running for the coldest 4 months of the year. That's ~ 1000kWh additional demand on your heating. Not enormous, but definitely not insignificant.

I think I agree with Petriix.

• A typical PIV flow rate is 20 litres per second. The heat capacity of air is around 1.2J/ltr/deg. C.
• If incoming air at 5C displaces air at 20C, each second you'll lose (20 x 1.2 x 15) 360J. That's a 360W heat loss.

Gerry1

Presumably the answer would be to switch off (or reduce) the PIV's heater and mount it on the landing above a GCH radiator?  The rising warm air should prevent draughts (and you don't sit in an armchair on the landing all evening), so the heat loss would be met by the GCH at much lower rates and the extra cost would be lost in the noise.

Ignite

A question for those of you who are using a PIV.  How quiet are they?  Do you hear any fan noise?

digannio

Good points Gerry. In our case the diffuser is in a central hallway on the ceiling and there is a radiator not quite below it but very close. There really isn't an icy blast hurtling through the home and causing the heating to be on 24/7. I've turned off the heating element on the PIV which I felt wasn't worth the extra costs after I was switched to Octopus and had a huge rise in energy charges. The PIV still works well in eliminating condensation and doesn't impact on heating costs.