Positive input ventilation units

[Zep]

Does this work on leaky creaky old timber-framed houses as well, Zep?

It does, as the outdoor air is very dry, you do need some heat to recover or the whole thing fails. As a large stadium found a few years ago!

 

[CatmanV2]

Which begs the question

In my dreams

C

 

[Navcorr]

In my dreams

C

Should've played this instead

 

[CatmanV2]

C

 

[Gazcw]

This sounds like a more sophisticated (and therefore expensive) system than the Nuaire, which I thought just take air from outside, or have I misinterpreted?

They use the warm air being pulled out to heat the outside air coming in. Had one in my 1820's cottage and worked a treat. Had mould up the backs of wardrobes until it was fitted. After, all was good.

 

[Zep]

This sounds like a more sophisticated (and therefore expensive) system than the Nuaire, which I thought just take air from outside, or have I misinterpreted?

It is. Would a basic fresh air system like the nuaire work to reduce the condensation? Yes is the short answer. The slightly longer answer is yes, but it will cost you. As this works by bringing in cooler, drier air from outside the cost to you is the energy for the fan (not much) and the energy to heat the air back up to the temperature you want it to be. Lets throw some maths at it and see where we come out.

The Nuaire unit moves between 15 and 60 litres/second of air. Lets assume it generally runs at 40 litres a second. Then lets assume that the air being supplied into the house is on average 15 degrees colder than you want it to be and that the humidity at 5 degrees is around 70%. It will take roughly 15 kJ of energy to heat 1 kg of this air from 5 degree C to 20 degrees C measured on my trusty psychrometric chart. 40 litres of air is around 0.0496 kg. Over 6 months - the period when condensation might be an issue (182 days) the unit will move 779950 kg of air. 15 kJ x 779950 kg = 11699251 kJ or 11699 mJ. 11699 mJ is 3249 kwH. Assuming you heat your house with gas and have a high efficiency boiler (90% efficient) then you will need 3610 kWh of gas to heat this air. At the average UK cost of gas at 3.8p per kWh, it will cost roughly £137.18 per year to heat the air brought in by the unit. So over the 15 year life of a device like this, it will cost around £2,000 in extra heating costs, before you allow for any increase in gas prices over the next 15 years. If the unit were heat recovery instead the heating cost would be about 8% of this figure, about £10 per year.

 

[2b1ask1]

Or get yourself a menopausal woman; she will both heat the house and make sure it is very well ventilated!

 

[hunta]

It is. Would a basic fresh air system like the nuaire work to reduce the condensation? Yes is the short answer. The slightly longer answer is yes, but it will cost you. As this works by bringing in cooler, drier air from outside the cost to you is the energy for the fan (not much) and the energy to heat the air back up to the temperature you want it to be. Lets throw some maths at it and see where we come out.

That's not even man-maths. Moderator, is that even allowed on this forum? Oh...

£2k over the life is an interesting figure as my rough Google-based estimate has that kind of number as the initial outlay differential. Given the shonky build I have no confidence in its thermal retention qualities, which I understand is also a factor.

 

[Zep]

That's not even man-maths. Moderator, is that even allowed on this forum? Oh...

£2k over the life is an interesting figure as my rough Google-based estimate has that kind of number as the initial outlay differential. Given the shonky build I have no confidence in its thermal retention qualities, which I understand is also a factor.

I know, who knew there was a sort of maths that isn't man-maths....!

You are right, there are a few other factors that will impact the calculations, this is rough and ready. If you have a lot of heat loss into the loft then the cost would go down, but then you should consider increasing your insulation. Also when it is really cold outside (and in your loft) you will probably also feel the draught from the cold air coming in. But the message is clear, and I see it all of the time, there is no such thing as a free lunch. If you go for something cheaper you will pay in the long run. Given the likely compound increases in energy costs which I haven't factored in, the operating cost is likely to be much higher, and so if you can, you should go for the most efficient option you can.

 

[Felonious Crud]

It's clear, Zep, that I need to buy you a pint and pick your brains. Probably not in that order, though. I'll be needing to take notes.

 

[Zep]

It's clear, Zep, that I need to buy you a pint and pick your brains. Probably not in that order, though. I'll be needing to take notes.

Oh I don't know, I would probably still make a bit of sense after one pint....!

 

[Felonious Crud]

Oh I don't know, I would probably still make a bit of sense after one pint....!

Oh, I don't understand anything after zero pints, regardless of who did or didn't consumed them or whether I'm not I'm the recipient or dispenser of subsequent sage advice. The world and its workings is a daily mystery to me.

I suppose all I want to understand is which option is best for cost and which is best for effectiveness in a creaky old L-shaped house with a large loft, albeit pretty well insulated between house and loft). Will I need a calculator?

 

[Mattp]

My dad used to do DPC and fitted lots of Drimasters, had one in my terrace which suffered condensation, cleared that right up... only issue I had was in the winter when the loft was very cold, you could feel the chill in the stairwell where it was... plus uor loft didnt have a proper firebreak so when my neighbour cooked anything really delicious - often on a sunday you could just catch a hint of it in the air!

 

[Zep]

My dad used to do DPC and fitted lots of Drimasters, had one in my terrace which suffered condensation, cleared that right up... only issue I had was in the winter when the loft was very cold, you could feel the chill in the stairwell where it was... plus uor loft didnt have a proper firebreak so when my neighbour cooked anything really delicious - often on a sunday you could just catch a hint of it in the air!

Exactly this, condensation goes away, heating bill goes up. You pay your money and pay your choice.