Housing - Renovation: Ventilation solutions for a gradual eco-renovation

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- CommentAuthorgravelld
- CommentTimeJan 28th 2015 edited
We don't have enough money to do the whole eco renovation in one hit. So we are going to have to improve energy efficiency of the house in bits and pieces.

I want to start addressing ventilation. RH in many rooms is consistently around the 70% mark; I want to get this down to 60% as a maximum. Condensation is a problem and as I have been draught proofing we are beginning to see mould on window frames and in window reveals.

The house, despite my air tightness work so far, is probably still (air) leaky. So what is the best methodology to go forward? Should I try to start an MVHR project, knowing it's going to cost us while the house is leaky? Should we go for SRHRV and do rooms as and when?

Some house details:
- 1950s build, masonry cavities
- All cavities filled, although some with fibrous batts
- Cold roof, 270mm rockwool
- Zoned heating, only 40% of the house is heated typically
- Three (count 'em!) extensions
- Three bathrooms, two toilets, all dumb 'hole in the wall' extraction (although I did install an Iris fan in one toilet).
- One kitchen, one utility room, neither with extraction or cooker hood filter
Any thoughts would be appreciated, I'm not expecting one true answer but more a bit of guidance as to what to look at, what to measure etc.
- CommentAuthoratomicbisf
- CommentTimeJan 28th 2015
What about installing the ducting for MVHR room by room as you refurbish them and in the meantime use a dehumidifier where necessary? That is what I have been doing.

Ed
- CommentAuthortony
- CommentTimeJan 28th 2015
The best way to reduce humidity is at source see for some advice http://readinguk.org/draughtbusters/?page_id=427

Dehumidifier will help if you still have problems.

The Robles with not heating some rooms is that they act as dehumidifiers and the condensation is drawn to them like a magnet.
- CommentAuthorgravelld
- CommentTimeJan 28th 2015
Pretty sure we're doing everything we can to reduce humidity at source, other than not drying clothes indoors as I downright refuse to purchase a tumble drier. Would prefer a drying room with heat recovery ideally. Generally I don't see a huge difference in RH when clothes are being dried anyway.

The bathroom we mainly use has an under speced extractor hole in the wall... This is not even desirable short term, long term it cannot possibly be acceptable.

Getting tired of opening the window for two hours and losing much of the house's heat through it.

I feel others may be in the same situation as me and don't have the capital to do everything at once. So what are the best 'small steps'? Or am I asking the impossible?

Ed: I am clearing out the loft this summer so it could be a time to run ducting (but that requires a lot of design and planning) or install new point solutions in the first floor wet rooms. Nice idea, how much doors the dehumidifier cost to run?
- CommentAuthorGotanewlife
- CommentTimeJan 29th 2015
Not read it yet but latest Which mag incl dehumidifier test.
- CommentAuthorcjard
- CommentTimeJan 29th 2015 edited
If your house is leaky then some humidity source is the world (the outside air). You cannot reduce this (you cannot reduce the humidity of the world; you just accept tht if you let that air into your home, then you accept the moisture that comes with it, unless you want to get into air con and altering its humidity on the way in). Relative humidity is exactly that- relative. Warm air holds more moisture, so heat the air and the relative humidity will fall. As others note, cold spaces act like dehumidifiers. A surface below twelve degrees c will be liable to condensation, and single figures a virtual certainty if air that is "comfortable to live in" comes into contact ith it. Drawing the curtains at night makes the problem worse.

Buying a tumble drier doesn't have to be the devils work as an interim measure, especially condensing heat pump (CHP) ones. A CHP drier is a 600mm box version of your dream house; air tight and heat recovering. Any escaping heat (from the drier) is in the house still, unlike a vented drier.

Have a search for some threads on the forum about DIY leak testing by mounting a car radiator fan in plywood and replacing a window pane with it, depressurise the house and go leak hunting with wet back of hand or smoke pen. Right now as others say you'll need to tackle moisture generation mechanically by some means, heating, dehumidifying.. Otherwise your cold house parts will continue to act as dehumidifier. Could always use a window vacuum (search screwfix for window vaccum) if you don't want to get a dehumidifier. Installing m v h r as you go is an idea but really is a whole house solution to a whole house problem. If you don't use 60% of the house then seal those parts off draft wise [and thermally] and leave windows open in the rooms that are sealed off (reduces the size of your house to just what you use, conceptually) if the moisture problem is getting really bad and you don't want to heat those parts
- CommentAuthorcjard
- CommentTimeJan 29th 2015 edited
Dehumidifer running costs are similar to a fridge - same idea you see. The fridge cools the interior by cooling a plate. The frdge air temp falls, becomes 100%RH saturated and water condenses on the cool plate. A defrost cycle sees the water run off and down a drain to sit on top of the warm compressor and be driven off. The back of the fridge warms up and this heat is lost to the air in the house, as it must be for the heat pump cycle to keep functioning

A dehumidifier cools a plate, it passes warm moist house air over the cool plate causing the humidity to reach saturation in the cool air and it condenses on the cool plate. Periodically the plate defrosts and water is collected and not evaporated. The cool plate is cooled by a heat pump, that pumps the heat to another plate. The air exiting the dehumidifier passes over the hot plate and warms up again. Water has already been lost from the air so the air relative humidity is lower then when it entered the DH.

Hopefully this explains how a DH is just like a (fan powered) fridge. They run a fan constantly but their cooling plate and heat pump system is smaller so less consuming- overall this makes them similar in cost to run as a fridge
Certainly cheaper than repairing the damage mould and condensation cause
- CommentAuthorNick Parsons
- CommentTimeJan 29th 2015
cjard, I have been doing my best to 'de-code' a couple of bits of your post, but cannot!

I think I get the sense, but cannot work out what the words were necessarily meant to be!

What should the word be instead of 'world' at the end of the first sentence? 'Hating' for 'heating' I get, but in the sentence after, ('Otherwise your cold house pats with....'). Is that 'otherwise your cold house parts will...'?

Yours, Intrigued of Sheffield!
- CommentAuthortony
- CommentTimeJan 29th 2015
If the house is warmer than outside then RH will virtually always be lowered by air leakage and ventilation.

Can you tell us air temperatures and humidity readings for 6 or 8 main rooms please?
- CommentAuthorrhamdu
- CommentTimeJan 29th 2015
Posted By: cjardDehum costs similar as a fridge, Same idea you see
and even the desiccant type are similarly priced, though I think they may come down as the technology matures. I guess they may also come closer to the efficiency of compressor-type DH.

(Main reason for choosing a desiccant DH, despite the higher electricity consumption, is that they perform better at lower temperatures. I just left a modest 8-litres-a-day model running for 5 days in an unheated flat. Came back and it had filled a plastic builders' tub with water.)
- CommentAuthorgravelld
- CommentTimeJan 29th 2015 edited
Thanks everyone. DH definitely on the radar if it helps short term and plays into the longer term plan. Advice welcome on that. Looks like desiccants are best, will try to calculate what's best given an expected period of use (in years).

Posted By: Nick Parsonscjard, I have been doing my best to 'de-code' a couple of bits of your post, but cannot!

"CHP drier" too - combined heat and power drier? Google doesn't turn up much.

Posted By: tony
Can you tell us air temperatures and humidity readings for 6 or 8 main rooms please?

Heated rooms: kitchen, lounge, two bedrooms. Generally no higher than 19C (lounge goes up to 22C and heats hallway and landing too to about 16C when stove is on). Drop to about 16C overnight (second bedroom drops further as detailed here: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12874 [how do I get a link working in HTML formatted comments? Anchors don't appear to work].

Unheated rooms: range from about 9-12C (at current ambient temperatures). That's bedrooms, one "sun room", dining room, hallway and landing (when stove is off) and a bathroom.

Right now I only have humidity readings for the coldest bedroom which is the one that hovers around the 70% mark. Lowest I have seen is 61% when I opened the window. Highest is 76%. Shall I get more data?
- CommentAuthorcjard
- CommentTimeJan 29th 2015 edited
Posted By: Nick Parsonscjard, I have been doing my best to 'de-code' a couple of bits of your post, but cannot!

I edited the post to correct it - sorry.. writing long posts on an iphone 4 is a problem; the phone UI gets ever more sluggish as the post gets longer and the phone autocorrects to what it feels like with fingers the size of mine; Far prefer my windows phone as you type by swiping around the keyboard and it's generally more accurate

I do think the keyboards should have been redesigned for phones; qwerty is just stupid because 3 vowels (U I O) are all adjacent (and right against the edge of the screen) making them easy to mis-key..
- CommentAuthorcjard
- CommentTimeJan 29th 2015 edited
Posted By: gravelld

"CHP drier" too - combined heat and powerdrier

Well I *had* literally only just said "condensing heat pump drier" 4 words previously, but you're right - I should have defined the acronym clearly before use.. :) ;)
- CommentAuthorrhamdu
- CommentTimeJan 29th 2015
Nobody has suggested single-room MVHR. I haven't tried it so I don't know the pros and cons. But it should be one of your options, even if you end up deciding against.

Meanwhile, a dehumidifier (plus an advancing programme of insulation) should sort out your short-term condensation problems, and you will then only need enough ventilation to ensure air quality.

By the way, I'm not saying desiccants are best. Only that they work well in cold rooms. Horses for courses. I'd probably go for a compressor DH (lower electricity bill) if it was to be used in heated living space.
- CommentAuthorcjard
- CommentTimeJan 29th 2015
Posted By: rhamduNobody has suggested single-room MVHR (SRMVHR). I haven't tried it so I don't know the pros and cons. But it should be one of your options, even if you end up deciding against.

They can be pretty pricey, mind.. I got the impression the OP is doing this work gradually because just dropping 10 grand on insulation and MVHR isn't an option. The SRMVHR I've seen are a couple of grand just for the unit.. Compare that to the 75% efficient mini MVHRs floating round ebay for Â£170 quid and...
- CommentAuthorSteamyTea
- CommentTimeJan 29th 2015 edited
Posted By: cjardI edited the post to correct it - sorry.. writing long posts on an iphone 4 is a problem;
You would think that with $18bn (Â£11.8bn) sloshing around in the bank that Apple could sort this. Maybe a physical personal assistant for each customer to take notes.
Apple has made the equivalent of $1.70 off every person on the planet. A days wage in some place, that is obscene.
- CommentAuthorandyman99
- CommentTimeJan 29th 2015
I can commiserate, squeegeeing windows is my start of day routine!

Iâ€™ve been monitoring humidity levels closely for 11 months. We have been increasingly vigilant in not producing moisture internally. We are 2 people in a 5 bed house. I do all the washing and it is never dried inside. Cooking is now closely monitored, some steam is inevitable, but it really is kept to a minimum. After showering we open the window/extract quickly. It is an all tile room including the floor, so very little comes vapour is retained â€“ I check with a humidity gauge! Note I should say that I have spent 2 years sealing as many holes as I can find, the house is certainly a lot more airtight than it was.

Currently the main kitchen/living area is 16 degrees and 63% RH. I havenâ€™t opened windows or used my de-humidifier here for 2 weeks. Hmm so this is not typical of what I have been seeing over most of the 11 month period, where humidity would have been steadily climbing without some form of intervention. Wall construction is only brick, 50 mm cavity filed with beads, and block work. The last 2 months have been the only prolonged period of typical cold dry winter weather whilst I have been monitoring (mid-south England). The only explanation I can think of is that the external cold dry air is still being exchanged through the walls of the house. (I know this is not really my idea â€“ others have mentioned this) but not through gaps.

So in the bedroom the humidity does rise more from the occupants, the DG windows are relatively poor may be 15 years old and PVC etc. Any time the external temp falls below about 7 degrees there will be condensation. The increased airtightness along with pleated blinds has definitely made things worse (humidity) but heat retention is improved. Iâ€™m not sure how low I would have to get the humidity to stop condensation, but there seems little point if your efforts are undone the next time external conditions change.

Now my theory on opening windows in this situation, is that, if you open for a long period, you lose a lot of heat and of course also exchange the wet air. But because of the buffer effect, as soon as you close the windows it all comes back out of the woodwork and the levels soon rise again. So really you want to open windows for a few minutes until the level drops then close, then reopen again! Sort of mimicking MVHR but not really practical unless you are really sad.

Iâ€™m not prepared to fit MVHR (although would if committed to house long term), but I wouldnâ€™t be surprised if new glazing and further insulation would be need to completely eradicate the problem.
- CommentAuthorgravelld
- CommentTimeJan 29th 2015 edited
Posted By: rhamduNobody has suggested single-room MVHR. I haven't tried it so I don't know the pros and cons. But it should be one of your options, even if you end up deciding against.
I did! I wonder whether they might actually form part of the ultimate solution in MVHR is not practicable, so it's on the table. Also of consideration (although I'm not sure if these even exist) are hybrids where wet rooms are coupled with dry ones. Might work with zoning better... but I'm not sure if these even exist (just buy cheap MVHR for smaller spaces?).

Posted By: cjardThey can be pretty pricey, mind.. I got the impression the OP is doing this work gradually because just dropping 10 grand on insulation and MVHR isn't an option. The SRMVHR I've seen are a couple of grand just for the unit.. Compare that to the 75% efficient mini MVHRs floating round ebay for Â£170 quid and...

By SRHRV I thought I meant the units that are about Â£200 e.g. https://www.google.co.uk/webhp#q=vent+axia+hrv&tbm=shop

Â£10k for insulation and MVHR? It will be more than that. Just EWI will likely by Â£20k I think, add the windows that "should be done" at the same time - another Â£20k...

Posted By: rhamdu
Meanwhile, a dehumidifier (plus an advancing programme of insulation) should sort out your short-term condensation problems, and you will then only need enough ventilation to ensure air quality.
With CWI already done, I'm not really sure where insulation can go next other than EWI. The house is rendered and we will seriously consider EWI when that comes... and replace the windows at the same time (old 2G, U=3ish where most of the condensation collects). But as above that's going to be a lot of money... money I'm not entirely sure from whence it will come.

Posted By: andyman99
Iâ€™ve been monitoring humidity levels closely for 11 months. We have been increasingly vigilant in not producing moisture internally. We are 2 people in a 5 bed house. I do all the washing and it is never dried inside. Cooking is now closely monitored, some steam is inevitable, but it really is kept to a minimum. After showering we open the window/extract quickly. It is an all tile room including the floor, so very little comes vapour is retained â€“ I check with a humidity gauge! Note I should say that I have spent 2 years sealing as many holes as I can find, the house is certainly a lot more airtight than it was.
How long does it take to dry clothes in this weather? Also bear in mind we have a 1yr old.

I find squeegy-ing after showering makes a big difference. Also having the shower cold, but I'm the only one that does that

Posted By: andyman99Iâ€™m not prepared to fit MVHR (although would if committed to house long term), but I wouldnâ€™t be surprised if new glazing and further insulation would be need to completely eradicate the problem.
I am prepared for that - the idea this is a 25 year house at least. At least until we self build a retirement house. But as above I'm not sure where else insulation can go... insulating the window reveals and onto the frames maybe. But I don't want to do IWI, seems not-as-good-a-job as EWI.

Stepping back to ventilation, I feel I want some form of heat exchanging ventilation, with the opportunity to increase indoor air quality. So it feels like MVHR, SRHRV or some hybrid is ideal. The question is how to balance costs, disruption and temp zoning (see thread on MVHR zoning). Also balancing wrestling with building control... currently in an email exchange with them about whether they would allow windows without trickle vents if ventilation was whole house and controlled. They don't seem keen. If I commit to one solution, I may find myself unstuck later due to such regulations.

Sometimes I wonder whether I read great sites like this about what is possible and lose sight of what is practicable (although different people have different definitions of that word).
- CommentAuthorPile-o-Stone
- CommentTimeJan 29th 2015
Posted By: atomicbisfWhat about installing the ducting for MVHR room by room as you refurbish them and in the meantime use a dehumidifier where necessary? That is what I have been doing.

Ed

This is what we are doing as well. We installed new double glazing throughout the house and we're currently installing IWI and ducting for the MVHR on a room by room basis. Since the new windows were fitted we noticed a huge rise in condensation on the exposed stone mullions that frame the windows and on cold spots on some of the external walls where the plaster board 'dot and dabs' are located. It'll be years before all of the IWI and ducting is complete, so we've decided to be pragmatic and buy a dehumidifier and put up with the costs of running it. Once the IWI and ducting is complete we'll put the dehumidifier on ebay to recoup some of the costs.

Its a good solution with a lot of water being taken out of the air and poured into the drain (some is retained for the iron). Our condensation issues have all gone and the windows are dry and mould free. Any increase in our electricity bill will add to the motivation to get the IWI and MVHR installed ASAP! :)
- CommentAuthorNick Parsons
- CommentTimeJan 29th 2015
I did a survey on a barn conversion a few years back, and noted condensation on stone mullions and adhesive dabs, like you did. What I was not prepared for, however, was the *ice* where the condensation had frozen on the inside of the stone door frame!
- CommentAuthorPile-o-Stone
- CommentTimeJan 29th 2015 edited
Posted By: Nick ParsonsI did a survey on a barn conversion a few years back, and noted condensation on stone mullions and adhesive dabs, like you did. What I was not prepared for, however, was the *ice* where the condensation had frozen on the inside of the stone door frame!

We also had ice forming on really cold days, despite having the central heating on. The ice and the white mould that was starting to form finally pushed me to buy the dehumidifier. I'm now in the 'design phase' of fitting earogel insulation to the stone mullions to prevent the condensation forming.
- CommentAuthorcjard
- CommentTimeJan 30th 2015
No swype for iOS alas. Use the equivalent on. Y windows phone tho. Is good

Apple is sitting on 142billiom I doesn't know what to do with apparently. They we're forced into buying back some shares with some of it but it didn't rally help. http://m.bbc.co.uk/news/business-31016446
Too bad Steve jobs was a miserable butger who never followed gates and buffet's lead into the giving pledge
Certain that most of the problems are due to it being an old phone now and quite slow coupled with some poor design aspect of this page causing the browser to chug. I can mostly get my point across tho :)

The 10k wasn't a quote ;) tho I dare say I'm hoping to mvhr and king span my house for about that sum. Wei mght we'll be expensive, I'm going iwi instead
- CommentAuthortony
- CommentTimeJan 30th 2015
You should be able to fit a whole house fan box in the loft and add ducts as to go. plan the system and leave blanked off tees in the right places

it would work OK with just two connections to the house and the maim intake and exhaust to/from outside. variable speed controller
- CommentAuthorrenewablejohn
- CommentTimeJan 30th 2015
Posted By: rhamduNobody has suggested single-room MVHR. I haven't tried it so I don't know the pros and cons. But it should be one of your options, even if you end up deciding against.

.

This is the route we are going down in our Listed Building. By putting sealed 3G units in without any opening windows we had to design a MVHR to protect the fabric of the building which will be achieved by using 7 Partel MVHR units in each of the en-suite and kitchen areas. Living rooms ventilated by wood burning stoves.
- CommentAuthorgravelld
- CommentTimeJan 30th 2015
Posted By: tonyYou should be able to fit a whole house fan box in the loft and add ducts as to go. plan the system and leave blanked off tees in the right places

it would work OK with just two connections to the house and the maim intake and exhaust to/from outside. variable speed controller
So size it for the whole house and just add ducts as and when? Just need to design the system, small matter

Also talking to BC about how they treat MVHR that isn't in all rooms. I initially asked regarding trickle vents (the house has a few windows with them and the standard position, as we all know, is that if replacing windows with trickle vents the new ones have to have them too) and once I brought up the MVHR acronym they said there'd be no requirement for them. But I'm not sure if they thing that means every room, or at least every room with trickle vents, has an inlet/outlet.

Posted By: cjardThe 10k wasn't a quote ;)
When can you start?
- CommentAuthorjules
- CommentTimeJan 30th 2015
What are you planning to do with the windows? My house has 15 yr old UPVC 2g, and since the frames are in good condition I had thought about waiting, and eventually replacing with 3g when that comes down in price. But condensation problems in our bedroom (3 outside walls, 5 windows) persuaded me to replace the glazing in 6 windows in total, for a cost roughly the same as the quote for replacing just one of the windows in its entirety.

I have only just done it, but so far the higher surface temp of the new glazing has made a defnite difference to the amount of condensation on the windows, and hopefully in time to the problems of mould in the window reveals etc. If you replace the units yourself, that might be an option even if only on the windows with the worst problems, compared with waiting several years until you can afford to replace the entire windows.
- CommentAuthorandyman99
- CommentTimeJan 30th 2015
Jules - timely post, I had been mulling over this very same idea. Also have a 3 external walled bedroom with 5 windows and about 15yr old DG. Any idea what sort of spec your new windows are? How much improvement has it made would you say?
- CommentAuthorjules
- CommentTimeJan 30th 2015
Andyman
Too early to say about the improvement because I only finished this week, and because of the weather the air has been quite dry recently so there's less condensation generally. But obviously there are two effects: higher glass surface temp, and also less heat loss overall and hence a warmer room. In our case this is a dormer in a roof with lowish ceiling, so the windows are quite a high proportion of the surface area.

My new glazing spec was:
21x 28mm double glazed units â€“ 4/20/4
Argon
Soft coat low-e
Warm edge spacer bar (black)
Centre pane u-value approx 1.2

I had requested "the lowest u-value you can do". I thought it was possible to get a u-value of 1.1 these days, but I haven't found it.

To save money I did the original measuring and then collected and replaced the units myself: I would have had to get someone in to replace whole windows, which obviously affects the relative cost. In theory replacing the units is straightforward, but I think uPVC gets more rigid as it ages, because I found removing and especially replacing the internal beading was a ****er.
- CommentAuthorNick Parsons
- CommentTimeJan 30th 2015
How much improvement?

Multiply up. U value x area x duration of heating period:

Old DG with maybe 15-16mm spacer and plain glass might give around 2.5W/m2K, and modern unit with soft-coat low E, 16mm gap, warm-edge spacers and argon nearer 1.6 (whole unit - U(w), with perhaps 1.2 centre-pane U value - U(g).

It is not only about the improvement in fabric U value, though. Warming up the windows may reduce convection currents, and thus reduce cold draughts.
- CommentAuthorgravelld
- CommentTimeJan 30th 2015
Posted By: julesWhat are you planning to do with the windows? My house has 15 yr old UPVC 2g, and since the frames are in good condition I had thought about waiting, and eventually replacing with 3g when that comes down in price. But condensation problems in our bedroom (3 outside walls, 5 windows) persuaded me to replace the glazing in 6 windows in total, for a cost roughly the same as the quote for replacing just one of the windows in its entirety.

I have only just done it, but so far the higher surface temp of the new glazing has made a defnite difference to the amount of condensation on the windows, and hopefully in time to the problems of mould in the window reveals etc.
We sound like a similar situation - old style 2G, except timber, about 6mm, U=3ish as far as I can tell. We also have newer 2G with wider gaps and non metallic spacers, but not many, probably 15% of all windows.

The plan to replace all of these was to do at the same time as EWI which was to be done at the same time as re-rendering, which would be the one "big splash" of cash we would have to make and would hopefully be five or so years off.

I am hesitant to simply replace the glazing because we also get condensation and mould on the casement timbers.

It's worth having a look at though, I need to model the house including window area so I can run the numbers.

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Housing - Renovation: Ventilation solutions for a gradual eco-renovation