Ventilation

[Distinterior]

This house had an MVHR system fitted. It was a very large room and if I remember correctly, there were 3 or 4 duct inlets for the system in the room....

You can see one of the ducts in the picture and there is another one on the other side of the ceiling bulkhead that I built for the remote controlled extractor hood.

 

[Woody2Shoes]

You can get single room mvhr units for kitchens and bathrooms. They really need to be mounted on an external wall. By the sound of things your kitchen, laundry and bathrooms would be the most important places to start on.
Cheers, W2S

 

[Woody2Shoes]

eg https://www.vent-axia.com/range/single- ... overy-srhr

 

[Rorschach]

how much (roughly) would a unit like this cost and what is the payback time?

It's not so much a unit as a system. It's basically a couple of fans in a plastic box, lots of ducting, and some very basic controls. To buy all the kit to DIY fit in a 4 bed detached property was around £2000 to £2500 when I looked recently. The expensive part comes when you pay someone to crawl around in your loft running the ducts and fitting everything....but for any competent DIYer that should take a couple of days at most. It needs a lot of thinking about, because the pipe runs can be complex.

Ok so lets say £3000 minimum. How long would the payback be on that? Several decades at least. I think I would rather spend that £3000 on a high quality dehumidifier and a lifetimes worth of electricity to run it.

 

[Woody2Shoes]

how much (roughly) would a unit like this cost and what is the payback time?

It's not so much a unit as a system. It's basically a couple of fans in a plastic box, lots of ducting, and some very basic controls. To buy all the kit to DIY fit in a 4 bed detached property was around £2000 to £2500 when I looked recently. The expensive part comes when you pay someone to crawl around in your loft running the ducts and fitting everything....but for any competent DIYer that should take a couple of days at most. It needs a lot of thinking about, because the pipe runs can be complex.

Ok so lets say £3000 minimum. How long would the payback be on that? Several decades at least. I think I would rather spend that £3000 on a high quality dehumidifier and a lifetimes worth of electricity to run it.

The single room jobbies start at around 300 ukl and are a relatively simple retrofit.

 

[John Brown]

how much (roughly) would a unit like this cost and what is the payback time?

It's not so much a unit as a system. It's basically a couple of fans in a plastic box, lots of ducting, and some very basic controls. To buy all the kit to DIY fit in a 4 bed detached property was around £2000 to £2500 when I looked recently. The expensive part comes when you pay someone to crawl around in your loft running the ducts and fitting everything....but for any competent DIYer that should take a couple of days at most. It needs a lot of thinking about, because the pipe runs can be complex.

Ok so lets say £3000 minimum. How long would the payback be on that? Several decades at least. I think I would rather spend that £3000 on a high quality dehumidifier and a lifetimes worth of electricity to run it.

And I'd rather spend it a bit of extra heating to make up for the heat lost from a PIV system.
I just don't think ducting everywhere is going to work in this barn. It would have to be surface mounted and boxed in in some places. Added to which I don't have the budget for it while we still own the house we moved from.
I have a dehumidifier, that claims it can remove 20L per day. It works OK, but it's noisy, and has to be emptied every two or three days. And it's nearly 400 Watts. I'll connect a Watt hour meter to it and see what it averages out at over a week or so.

 

[MikeG.]

how much (roughly) would a unit like this cost and what is the payback time?

It's not so much a unit as a system. It's basically a couple of fans in a plastic box, lots of ducting, and some very basic controls. To buy all the kit to DIY fit in a 4 bed detached property was around £2000 to £2500 when I looked recently. The expensive part comes when you pay someone to crawl around in your loft running the ducts and fitting everything....but for any competent DIYer that should take a couple of days at most. It needs a lot of thinking about, because the pipe runs can be complex.

Ok so lets say £3000 minimum. How long would the payback be on that? Several decades at least. I think I would rather spend that £3000 on a high quality dehumidifier and a lifetimes worth of electricity to run it.

If you compare apples with pumpkins you'll get meaningless results.......particularly if you decide to just make your numbers up.

 

[Rorschach]

I didn't make up numbers, you said £2-2500, I added on a couple of days of labour and sundries for the fitting. I don't think that's an unreasonable number.

 

[MikeG.]

I didn't make up numbers.......

Yeah you did. You decided that the payback period was several decades, without any evidence. You decided that a lifetime's electricity and a lifetime's supply of dehumidifiers amounts to less than £3000, without providing any evidence. That's making numbers up.

Worse than all that, though, was comparing a machine for removing humidity in one place in a house to a system which provides ventilation for the whole house. Condensing airborne water vapour on a cold matrix does not equal ventilation.

 

[Rorschach]

Ok, well here are some numbers, if I run my dehumidifier at full pelt 24/7 at current electricity prices it will use £3500 worth in just over 10 years.
Now I don't run it for that long of course, a few hours a day during winter is more than enough and in my mind it's is 100% efficient, any excess energy is released as heat so I get heat and dry air.

As for ventilation, unless you are living in a super carefully built home you will have plenty of leaks that will provide more than enough ventilation, totally discounting things like extractor hoods, shower fans, opening doors and windows etc.

Heat recovery ventilation in anything but a super tight passive house is a waste of money in my opinion. Your money is better spent elsewhere on other eco projects and using some common sense to ventilate by opening windows when the weather is fine and using a dehumidifier when the weather is bad.

 

[MikeG.]

Ooooh my goodness, Rorsach. I have to deal with reality. I don't get to make stuff up like that.

 

[Rorschach]

Ooooh my goodness, Rorsach. I have to deal with reality. I don't get to make stuff up like that.

Ok give me some real numbers then :wink:

 

[John Brown]

Ok, I'm sorry I started this now. There have been a handfull of useful replies I suppose.
I realise I'd be better off with a totally sealed house and heat recovery, but that's not likely to happen. All the reviews I've read of PIV, including one from a Which magazine researcher have been positive (no pun intended).
I'll have to add some ventilation to the loft, but that's probably a good thing anyway, as it smells a bit musty up there if I don't venture up for a few days.
My Christmas wish( despite being an atheist) is that people who don't have relevant knowledge should maybe think twice before weighing in. It's too easy to lose sight of the original question in all the noise. Science and technology do move on, albeit slowly. Yes, I remember ice on the inside of the windows and nothing but coal fires for heating. So what? Very few of us would tolerate that today.
Once again, thanks to those who offered constructive advice .

 

[Setch]

FWIW, I have a friend with a 1950s maissonette which was plagued with mould on the exterior walls due to condensation. They got a an envirovent system, and it totally resolved the problem.

I was very sceptical, but they're delighted with the results. I sealed up the old airbricks and trimmed the doors for them so that air could circulate throughout the flat, as they haven't had to scrub mould since.

 

[John Brown]

Thanks.
SammyQ says he was sceptical as well. To be honest, so am I, but I reckon it's worth a try.

 

[SammyQ]

My Christmas wish( despite being an agnostic) is that people who don't have relevant knowledge should maybe think twice before weighing in. It's too easy to lose sight of the original question in all the noise. 

I totally agree John (sorry to change your quote slightly). I have long asked here for exactly that: experience, not opinion.

My bottom line is that my condensation problem, and the mould that it encouraged, has gone. Given the medical condition I referred to above, I am very relieved and grateful. This - PIV - was our simplest option and we chose it as it seemed to be the least costly of the 'established' company-based ones and the least work to install. This last variable was very important at this exact point in our lives, with other considerations I need not trouble the forum with.

It may be that there is a "better" way of doing it; in our circumstances, this was the best available and I am content that we made the right call for us here, right now.

Merry Christmas to you and yours. We will have all ours here on 25th morning.

Sam

 

[Rorschach]

Ok, I'm sorry I started this now. There have been a handfull of useful replies I suppose.
I realise I'd be better off with a totally sealed house and heat recovery, but that's not likely to happen. All the reviews I've read of PIV, including one from a Which magazine researcher have been positive (no pun intended).
I'll have to add some ventilation to the loft, but that's probably a good thing anyway, as it smells a bit musty up there if I don't venture up for a few days.
My Christmas wish( despite being an atheist) is that people who don't have relevant knowledge should maybe think twice before weighing in. It's too easy to lose sight of the original question in all the noise. Science and technology do move on, albeit slowly. Yes, I remember ice on the inside of the windows and nothing but coal fires for heating. So what? Very few of us would tolerate that today.
Once again, thanks to those who offered constructive advice .

Sorry for trying to help top you wasting your money. :roll:
Just like the others I cured severe mould issues and got condensation under control, I didn't need any fancy expensive tech to do it and didn't increase my heating bill either.

 

[John Brown]

To be fair, Rorschach, your dehumidifier is fancier tech than my proposed PIV, and running costs of a dehumidifier aren't zero.
If I was living here alone, I might be able to keep things under control with open windows and fans, and careful showering/cooking.
But we have one daughter and two grandchildren here permanently now, another daughter with one grandchild here for seven weeks (from Hawaii, where they've never heard of condensation) and the youngest one and her daughter here 50% of the time. None of them understand how a thermostat works. One used to set the toaster to max, then pop up the bread every ten seconds to see if it was done, because she thought it would save time. I need something relatively foolproof.

 

[SammyQ]

John, you have 2 PM's.

Sam

 

[Rorschach]

To be fair, Rorschach, your dehumidifier is fancier tech than my proposed PIV, and running costs of a dehumidifier aren't zero.

I dunno, a dehumidifier is pretty basic and it involves no drilling of holes etc, just plug and play.
Yes running costs are not zero but the excess energy is released in the form of heat so during the winter I consider it to be 100% efficient as it gives me heat and dry air.

I take your point though about my method being more complex, it involves some thought, planning and common sense. For me that is a price worth paying as we are on a super tight budget so I need to keep things cheap and easy. If I had the money I would crank up the heating and install ventilation but I can't afford that and it is incredibly bad from an environmental standpoint.