Ventilation

[MikeG.]

...... I would.....install ventilation but....it is incredibly bad from an environmental standpoint.

Rorschach, you're talking tosh. There is a time to stop digging, and you've well and truly passed that. You clearly don't have the first idea about this subject.

 

[Rorschach]

...... I would.....install ventilation but....it is incredibly bad from an environmental standpoint.

Rorschach, you're talking tosh. There is a time to stop digging, and you've well and truly passed that. You clearly don't have the first idea about this subject.

Educate me then, I have asked you to before. Explain to me how bringing in cold air isn't a waste of money and how it is environmentally friendly. I asked you to do this before, if you know what you are talking about, back it up, show me the environmental and financial benefits.
I love to learn new things and am happy to be proved wrong, but so far all I have heard is old tropes that don't stack up in our current zeitgeist.

 

[MikeG.]

........Educate me then, I have asked you to before..........

I charge £50 per hour.*

Explain to me how bringing in cold air isn't a waste of money and how it is environmentally friendly..........

All houses bring in outside air. They have to, otherwise we'd die of asphyxiation. In all houses in the UK in the heating season, what they bring in is colder than what they expel. It isn't what they bring in that counts, but what goes out. In the case of natural ventilation (ie drafts), what goes out is warm air. In the case of MVHR systems, what goes out is cold air.

If you could compare two notional identical houses side by side, one with draft ventilation (trickle vents and the like), and the other with a mechanical ventilation system with heat recovery (MVHR) [there is a non-mechanical alternative also with heat recovery, but that's a side issue], both with identical heating systems and settings, and identical users, the MVHR will have significantly lower heating bills plus higher levels of internal comfort due to the lack of cold drafts. It's essentially controlled versus uncontrolled ventilation, with the controlled ventilation recovering the heat from the outgoing air and passing it to the incoming fresh air. Fresh air, in an MVHR house, is warm, not cold.

The energy costs of an efficient domestic MVHR system in the UK in money terms is (or was, last time I looked) between £15 and £35 per year, typically. Thus, in financial terms they only have to save that much wasted heat before they have out performed a draft-ventilated building. Mine have always been at the lower end of those figures because I turn them off in the summer when we have the windows open. The higher figure is for houses where they are left on year round.

Whilst their primary purpose is air supply, they also have a condensate drain, which leads excess airborne moisture directly to a drain. You have no Expelair-type extractor fans in bathrooms and kitchens in a house with MVHR, yet will never get any steaming up of the mirror after a long hot shower, for instance. Go away on holiday for 3 weeks leaving everything tightly closed and your house is fresh smelling, not musty, when you get back. You never have to open a window, ever, in the winter. You can have a pack of wet dogs in the house and have no wet-dog smell.

.........all I have heard is old tropes that don't stack up in our current zeitgeist.

You now know better. Ventilation heat recovery is critical to the performance of low energy housing. In the future, it will be compulsory, no doubt. Your understanding of the technology, and maybe of the current zeitgeist, was lacking. Now that you know better you'll maybe take a look at Passivhaus and see that they almost always include an MVHR system as a critical part of their energy reduction programme.



*You owe me £25

 

[Woody2Shoes]

I think Mike's nailed it.

All houses need ventilation - the building regs rightly insist on it. The only essential difference between a PIV system and an MHRV system (whether whole house or single room) is that in the latter there is a heat exchanger which 'saves' most of the heat that you've already paid for (directly or indirectly) from being wasted.

In my case, our ensuite with a single-room MHRV, the heat exchanger is simply a bunch of plastic tubes (very like a handful of plastic drinking straws) - that's the only difference between it and a conventional extractor fan. Admittedly, the thing runs in 'trickle mode' all the time, besides being in 'boost mode' when the room is in action (as a conventional extractor would be), but I reckon that's about £10 worth of electricity per year max.

I don't know whether I save £10 worth of heating energy per year as a result, but I get no cold draughts (important when you've got nothing on!) and no condensation, plus knowing that I'm not needing to fire the boiler to replace lost heat (or at least 80-ish% of the time).

I also know that my electricity supply is not as carbon-intensive as my space-heating - for a given amount of useable energy.

Cheers, W2S

 

[Rorschach]

Thank you for the information there, but you missed out on a key point with the discussion here, you are talking about new houses built with these kinds of systems in mind or at the least built to a decent standard of air sealing and insulation.

The OP, and my comments, all refer to older houses, leaky, poorly insulated, poorly air sealed.

I am not advocating against using heat recovery systems if you need to install ventilation in a new house anyway. I am advocating that in an old house you are spending a lot money installing any extra ventilation when you could do something else that will be more cost effective in the short and long term.

 

[John Brown]

The OP, that's me, thinks his house is actually quite well insulated and airtight, as it happens. Certainly way, way better in thise respects than our previous Victorian house. But the conversion seems to have been done without regard for ventilation. The previous owners had actually put duct tape over the few trickle vents, and over the outside of some keyholes.

 

[Rorschach]

The OP, that's me, thinks his house is actually quite well insulated and airtight, as it happens. Certainly way, way better in thise respects than our previous Victorian house. But the conversion seems to have been done without regard for ventilation. The previous owners had actually put duct tape over the few trickle vents, and over the outside of some keyholes.

I thought you were implying the opposite, my apologies. However given the fact it is over 30 years old and a barn conversion I suspect it is not as well insulated or sealed as you might think it is. Comparing to a victorian house is not much help, I have seen better insulated and air sealed colanders :twisted: :lol:

 

[Rich C]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

 

[Rorschach]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

Did you read what I wrote? The dehumidifier is used instead of extra ventilation and they put out heat as well as drying the air, overall it would use less money, not more. :roll:

 

[Woody2Shoes]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

I'm not on mains gas. My electricity supply is much less carbon intensive than kerosene. A dehumidifier is different from a mhrv unit.

 

[Rich C]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

Did you read what I wrote? The dehumidifier is used instead of extra ventilation and they put out heat as well as drying the air, overall it would use less money, not more. :roll:

Yes I did, but given electricity is about 4 times more expensive than gas, why heat your house with electricity using a dehumidifier when you could heat the intake air using your central heating for less?

I'm not sure how getting part of your heat from electricity rather than gas is supposed to save money. Didn't you say your dehumidifier costs £350 a year to run? That doesn't sound like a saving to me, it would increase my electricity bill by about 80%.

 

[Rorschach]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

Did you read what I wrote? The dehumidifier is used instead of extra ventilation and they put out heat as well as drying the air, overall it would use less money, not more. :roll:

Yes I did, but given electricity is about 4 times more expensive than gas, why heat your house with electricity using a dehumidifier when you could heat the intake air using your central heating for less?

I'm not sure how getting part of your heat from electricity rather than gas is supposed to save money. Didn't you say your dehumidifier costs £350 a year to run? That doesn't sound like a saving to me, it would increase my electricity bill by about 80%.

Ok you really need to go back and read things properly. :roll:

 

[AJB Temple]

I have lived in a few barn conversions and live in one now. They tend to have unique characteristics compared with conventional houses. These include: very high ceilings and atrium spaces (bearing mind heat rises); large open plan areas; high internal volume; uneven timber frames (often with penetrations) that can be difficult to seal against. Many early barn conversions were done in a rudimentary way.

Thank you to the OP for starting the thread. It has certainly made me think. I don't have a condensation problem in our house, but I am converting another small adjacent barn and will look at a heat recovery and ventilation system, which I had not previously considered.

AJ

 

[MikeG.]

......The dehumidifier is used instead of extra ventilation and they put out heat as well as drying the air, overall it would use less money, not more. :roll:

Except of course, that this is nonsense.

 

[SammyQ]

Yes, for costing more Mike, no in that they do emit a modest amount of heat.

Sam

 

[Rorschach]

Yes, for costing more Mike, no in that they do emit a modest amount of heat.

Sam

Yep a few hundred watts worth depending on the type (desiccant produce more heat).
I meant it over all costs less to keep vents closed and use the dehumidifier and less central heating than it would cost to ventilate with cold air and then use extra heating.
I was not saying the heat from the dehumidifier is used instead of central heating, I was saying heat is a by product so you gain some warmth for the money spent on drying the air, but you also lose a lot less warmth by not ventilating.

It's ok though, people read what they want to read it seems and Victorian thinking persists.

 

[John Brown]

"Victorian thinking persists. "
That's a strange thing to say about a technology that apparently was first used 50 years ago.

 

[Woody2Shoes]

Given how much cheaper gas is than electricity, I think I'd rather fire the boiler for a PIV system than run a dehumidifier.

Did you read what I wrote? The dehumidifier is used instead of extra ventilation and they put out heat as well as drying the air, overall it would use less money, not more. :roll:

Putting any financial considerations apart, it's important to have fresh air (ie air changes) to get rid of excess CO2 and bring in O2 - this is why building regs are written as they are. I can't be the only person who's left the 'recirc' switch on in the car for too long and got dozy/headachey as a result. It's not just about removing excess water vapour from the air (hence the word 'ventilation')...

 

[SammyQ]

Yep a few hundred watts worth depending on the type (desiccant produce more heat

Rorschach, I find both of those statements sweeping, and possibly, incorrect. When I wrote "modest" that is exactly what I meant; a very small, insignificant in the context, not enough to change the overall thermal energy within the house. I was, of course, being a naughty pedant, to wig Mike slightly. Do desicant dehumidifiers use heat? The ones I am familiar with have all been small scale ones based on hygroscopic cyrstals...

Sam

 

[Woody2Shoes]

Yep a few hundred watts worth depending on the type (desiccant produce more heat

Rorschach, I find both of those statements sweeping, and possibly, incorrect. When I wrote "modest" that is exactly what I meant; a very small, insignificant in the context, not enough to change the overall thermal energy within the house. I was, of course, being a naughty pedant, to wig Mike slightly. Do desicant dehumidifiers use heat? The ones I am familiar with have all been small scale ones based on hygroscopic cyrstals...

Sam

The crystals get 're-charged', or presumably 'charged' in the first place, by heating?