Green Building Forum - keeping RH and T under control in a rented flat

keeping RH and T under control in a rented flat

runcyclexcski — Tue, 12 Jan 2016 19:45:20 +0000

Hi all,

I have relatively recently moved from the US (CA, VA, NY) to Leicestershire. Prior to the US, I lived in Russia; both countries have subsidized energy costs (enabled by however many wars they have to maintain, which is OT). A minor positive was that keeping a flat warm and dry in the winter was never an issue (no winter to speak of in CA anyway).

Now me and my partner are in a relatively well insulated (2006) 2-br rented flat which are are struggling to keep warm, fresh, clean and dry (seem to achieve only 1-2 out of the 4 at any one time). The air quality is important b.c. we both have asthma. The warmth is my partner's deal-breaker (I used to sleep in a hat when I lived by myself). I am generally good with DIY (w/o upsetting the LL), and generally know what's thermodynamically possible. E.g. a dehumidifier sounds too energetically expensive and noisy to run 24-7 (and good DHs... i.e. ones that do not smell like burnt plastic all the time, are not cheap). I hope there is a more elegant solution.

I would like to maintain at least 1 bedroom at 40 RH, and I already positively pressurized it with HEPA filtered air, via a 20 cm duct from another bedroom. But, on the whole, the flat is sealed to keep the warmth in. Combined with the European habit of drying clothing inside, it's a dampness and asthma disaster, even though the bathroom fan (unknown m3perhr, probably crappy) is on all the time... not sure where the air gets sucked in from ... may be the shared hallway or the oven vent).

A heat-recovery fan sounds like a good idea, but I am not sure where the best spot for it would be, or if I would even need more than one. One idea is to run the ducting from the balcony, via a hole in the balcony door (I know how to do it w/o upsetting the landlord). I would probably want the HR to be positively pressurized, so that I control where the air comes in from (e.g. not from the oven vent). I also I don't want the fan to draw the humid air from the bathroom into the rest of the flat, so I somehow need to balance the fan in the bathroom with the HR fan. But the bathroom has no windows, and its fan exhausts who knows where -- some shared duct may be, we are in the middle of a building. The cloth drying disaster can probably be solved by making a contained tent/cupboard, a non-heated fan inside, and exhausting it into the wild >> even more need for a positively pressurized HR unit. And no, my partner won't go outside in the cold to hang the clothing on the balcony :).

Any advice would be appreciated! The budget is 1,000 quid, can push it to 1500.

Cheers, and I apologize for the lengthy message!

P.S. There could be some kind of warning that there is no keep-alive javascript while the user is typing. I have the habit of typing in an editor, but others may not.

keeping RH and T under control in a rented flat

Peter_in_Hungary — Wed, 13 Jan 2016 05:52:20 +0000

Posted By: runcyclexcskiThe cloth drying disaster can probably be solved by making a contained tent/cupboard, a non-heated fan inside, and exhausting it into the wild >> even more need for a positively pressurized HR unit.

A reasonably sealed cupboard with a dehumidifier in it would be a better bet - or a condensing tumble dryer

keeping RH and T under control in a rented flat

cjard — Wed, 13 Jan 2016 06:44:06 +0000

Identify the sources of moisture generation and deal with those first- dry clothes in a tumble drier vented to outside or condensing, ensure cooker hood extracts to outside and use it, ensure bathroom fan extracts to outside (you said it's an input fan.. It shouldn't be). Ensure adequate ventilation is available eg did the glazier forget trickle vents? Better than trickle vents is controlled ventilation- small MVHR units are relatively cheap but quite a building process.

Keeping warm involves inputting heat and trying not to lose it. The more ventilation, the more loss. An MVHR recovers some of the lost heat. If you're both asthmatic, Im surprised you'd even contemplate living somewhere that didn't have one

Keeping the place clean is, I think, independent of all these ;) my deal works out well.. I fix stuff, she cleans up after me. Ymmv

I've not noticed it needed, as even if I write a lengthy post it gets prompted back to me if the session expired and I have the option to put username and password in as well as lengthy post.. I recall it taking 2 or three submissions to get it posted but hey ho..

keeping RH and T under control in a rented flat

djh — Wed, 13 Jan 2016 13:53:04 +0000

A few thoughts:

(1) there are a lot of buildings that weren't built to the regulations that they were supposed to be, so get an infrared thermometer or much better beg, borrow or steal an thermal imager and check the outside of the building for hotspots indicating missing insulation and suchlike.

(2) RH is generally thought to be OK between 30% and 60%, any lower gives itchy eyes etc and any higher can give mould, mites and other health problems. It's not clear whether you want to keep humidity less than 40% or greater than 40%? Keeping it exactly at 40% is probably a non-starter. This country is more humid than many; my house has never been below 45% and that's the lowest of any house I've lived in during the winter.

(3) Generally the easiest route to comfort is to turn the heating up and increase the ventilation. If you can do that as a start and succeed the problem then becomes just how to optimise the arrangements to minimise costs. (more insulation and airtightness, MVHR, reduce moisture generation, cheaper heat sources etc). Why is the flat not warm enough?

(4) MVHR needs a balanced flow. You can't do HR if the exhaust is via an independent fan in the bathroom!

keeping RH and T under control in a rented flat

runcyclexcski — Wed, 13 Jan 2016 14:16:17 +0000

Thank you, all, for the comments!

I should have posted margins on the 40%. Yes, it was a ballpark, +- 10% should be okay.

djh, great point on the IR imager! I will try to get/borrow one, and I have a IR thermometer (I run a small research lab).

Our heat source is a gas boiler and radiators. This probably can't change, unless I keep a propane tank on the balcony which is probably not cheaper, and may upset the development. Will install warm curtains, and just added reflectors behind the radiators.

Regarding MVHR units -- don't some of them claim a 90% efficiency? Or is this a misleading spec? I am yet to see inside of on MVHR... I expect to see a bunch of finned heat exchangers with air channels inside, but not sure if an exchanger can be 90% efficient... at infinitely slow air speed may be.

OK, so I need to balance the MVHR somehow with the bathroom... may be I can run my own small ducts into the bathroom. The place already has my filtered air ducts running up next to the ceiling, so two more should not hurt :).

Regarding the dehumidifier/tumbler drying to dry clothing -- these are both electric, and I find it wasteful in terms of energy/non_green. We only use the tumbler when an "emergency" pair of clean pants is needed. :) And I think the tumbler exhausts back into the kitchen, but I have to check.

In my experience, creating an air flow from a regular fan 20C (Room temp) is enough to dry a load of cloths overnight (which is fast enough). Hence the idea with a cupboard blowing on the outside and sucking from the inside... but that needs to be balanced with the MVHR now.

keeping RH and T under control in a rented flat

cjard — Wed, 13 Jan 2016 15:18:26 +0000

For an idea on how much water your load of wet washing holds, weigh it wet and dry - i'm betting a few litres. If your drying methodology takes that and dumps it into the air in the flat the walls will be crawling with it!

It sounds like your lifestyle is generating a significant excess of moisture; address this first before throwing technology at it

THe passivhaus institut measures a paul novus 300 at 93% I think, according to their criteria (which are different to the sap appendix Q) but suffice to say a heat exchanger with a large surface area will transport a significant majority of the heat from one side to the other. I think you might be disappointed if you opened one though; heat exchangers in some are little more than an accordion-looking block of paper sheets that counter/cross flow the air
It's all they need to be, there's no rocket science in putting a warm thing next to a cold thing and having the cold thing warm up and the warm thing cool down. The trick in getting better than 50/50 is the counter flowing. Google "countercurrent heat exchange" and find out why sharks don't freeze to death :)

keeping RH and T under control in a rented flat

ringi — Wed, 13 Jan 2016 15:28:08 +0000

Personally I would buy a "EcoAir ECO DD322FW Desiccant Simple Dehumidifier" and leave it running in the room you used for drying your washing, while the washing is drying. (No need to seal the room, just point the output of the dehumidifier at the cloths rack.)

The running costs will be low, as you will only have it on for a few hours a week.

keeping RH and T under control in a rented flat

djh — Wed, 13 Jan 2016 17:08:15 +0000

Posted By: runcyclexcskiOur heat source is a gas boiler and radiators.

I would have thought that a gas boiler should be able to put out enough heat to heat the flat as warm as you need even if you just opened the windows a lot to dispel the humidity. Does that work? Is there a fundamental problem with being able to heat the flat enough, or is it simply a matter of wanting to optimise the solution?

Another thought - it may well be worth using your IR thermometer to check temperatures in the corners of rooms and the ceilings and floors. There are some nasty ways of building that leave great big paths for external air to circulate through the hollows between.

keeping RH and T under control in a rented flat

runcyclexcski — Wed, 13 Jan 2016 21:18:24 +0000

We have a gas heater, but we only have it on two-three hours a day to save on energy. Our bill is about 40 quid a month. We are home only 10-12 hrs a day (including sleeping :) ). But we have heat on max during these 2-3 hours. I am now thinking if it's better to have heat on to maintain the place at +18C at all times, rather than cycling between extremes (and running into additional condensation?) Plus, we are probably OK paying 50+ more for healthy living.

Yes, my current drying methodology (dumping 1 litre of water into a sealed flat) is unacceptable, and will need to change. I will post pictures of my designs...

If indeed there are only paper sheets in these heat-recovery venting units that separate the two air flows, it's quite disappointing. Two low-power blowers (under 20W?), a box, some ducting, and pleated paper sheets should cost well under 100, not 200-300 quid that I am seeing. Plus, if a sheet breaks. adsorbs water, and or starts supporting mold growth, it's bad news. I hope at least some units use Al foil pockets. I found some drawings here, which look proper.

http://ecorenovator.org/forum/conservation/891-diy-ventilation-heat-exchanger.html

Any units out there that have metal -- Al/copper -- exchangers? Size/looks don't matter. I want to be able to steam-wash the entire thing if necessary (sans blowers of course).

It's a good point that the builder may have tried to save on insulation in hard-to-see places. I certainly see that they used copper piping wherever I can see, which immediately becomes cheap flexible plastic as soon as it gets behind a drywall. If a builder uses granite counter tops, it's always a bad sign. :) But hey, one can only get a mortgage for an existing crappy-inside-cute-outside house, rather than to build a not-yet-existing robust-inside-functional-outside house.

http://ecorenovator.org/forum/attachments/conservation/609d1266778299-diy-ventilation-heat-exchanger-4d4fddd2a945955e-jpg" >

keeping RH and T under control in a rented flat

runcyclexcski — Wed, 13 Jan 2016 22:35:20 +0000

BTW, I found this (UK-based!) company that makes exchangers in 'proper' materials (Steel, Al) in all shapes and sizes (cross-flow, counter flow) and even encloses them in plenums if needed! I would go for welded steel, b.c. it can be washed and abused. I will then just connect two low-noise (<30 db) blowers for air in and air out and have them on trickle 20-30W power at all times. Don't need fancy sensors to adjust speed. Will include a basic filter plenum for air in and adjust the flow rate of the blowers to compensate the pressure drop. I already have an anemometer. It's a weekend project, in my experience.

http://www.uk-exchangers.com/heat-exchange-products/air-to-air-heat-exchangers/

I suspect I can get 2-3 of these for the price of a turn-key unit (of an unknown content... probably paper pleats like you suggested). Every time I see pictures of happy babies when I click the 'specifications' page, it's a red flag. I only found cross-sections of units online that cost 1500+. I suspect they do not want you to see insides of lower-cost ones (I guess anything less than 1000 is considered low-cost).

keeping RH and T under control in a rented flat

cjard — Wed, 13 Jan 2016 23:29:14 +0000

You have some odd ideas. A small MVHR, verified in testing, would be around 300 for sure.. And yes it's a couple of fans in a box, so maybe it should cost Less, but thats not generally how things in this world are priced. People buy on an assessment of what it's worth to them, and if I spent 3 days messing around making the perfect MVHR, even at my lowly wages it wouldn't have been worn my time.. Better just go to work and buy one. Ymmv

The paper exchangers are thus for a reason, essentially to do with vapour transmission and hence not requiring a condensate drain. Google lossnay MVHR units for more info. Other exchangers can be plastic, metal etc. if you build your own, make sure you deal with the condensation. Do the calcs and balance the flows properly otherwise you just won't get the same benefits

It's normal practice in this country to use plastic pipe for the majority of a run, for a plethora of reasons. Plumbers generally support the "copper is proper" notion even going as far as to say that soldering is the only decent way to join pipes. It's self serving bullshit of course, helps keep them in a job being able to sweat a neat joint when any Joe Bellend can push a plastic pipe into a one way fitting. Apparently copper is more aesthetically pleasing hence visible parts are copper, but going to plastic as soon as its out of sight is imho better practice than copper all the way.. And I'm one of those plastic all the way Joes :)

Granite countertops are the sign of a bad builder? Are you crazy? They're about the hardest thing to get right when it comes to work surfaces. If you'd said the same about laminated chipboard maybe I'd agree, but I think we'll have to put this one down to eccentricity. Granite is a pig and takes ages. It's the hallmark of a quality kitchen, well fitted

Mortgages to build houses are available; I have one. I pay double what friends who just bought a Ricky tacky volume developer house pay in interest but I get to build something great. People here care little for how well a house it build and more about looks and location. It's a flaw for sure

keeping RH and T under control in a rented flat

runcyclexcski — Thu, 14 Jan 2016 00:55:52 +0000

"if you build your own, make sure you deal with the condensation. Do the calcs and balance the flows properly otherwise you just won't get the same benefits"

OK, will do!

We just had a plastic pipe joint fail behind a sealed wall in the bathroom which flooded the entire garage 2 floors below, unbeknownst to us (the leak was not visible to the outside). It's the law of small numbers but... I use push-fit air connectors at the lab all the time, but at least I like to be able to see them. An improper welding job can lead to a disaster, agreed.

Yes, I agree, things are priced at whatever people are willing to pay, especially for a 'new' technology coupled with the notion of being green, and pictures of happy fat babies. I am willing to give my money to high-tech stuff (no way how I can make a smartphone myself). But if something is within my area of expertise, why not. And will learn something along the way, as usual. And the eccentricity is always there, of course. :)

The Lossnay thing does look proper, and has the air flow I had in mind (100 m3/hr). It uses 25-micron paper. Cost is around 300, as you indicated, thanks for the tip!

http://www.orionairsales.co.uk/mitsubishi-electric-air-conditioning-vl-100u5-wall-mounted-heat-exchanger-240v50hz-462-p.asp

I had to google "ticky-tacky":
https://en.wikipedia.org/wiki/Little_Boxes

Funny, the wiki article mentioned La Honda, CA where I used to live.

keeping RH and T under control in a rented flat

cjard — Thu, 14 Jan 2016 07:08:06 +0000

Check whether that pipe had an insert in the end, some people skip on putting them in, usually a bad idea. You should also be able to tell from the teeth marks on the outer, where the pipe was inserted up to.. None of it helps now of course, but if the same plumber did the rest and adopted a policy of not using inserts/pushing them home properly you could have a few more disasters waiting to happen

keeping RH and T under control in a rented flat

DarylP — Thu, 14 Jan 2016 07:40:34 +0000

sligtly off topic, but the plastic inserts in the 'Speedfit' pipes can be the problem, not the solution to leaks!
If the end of the pipe is not 'square' the insert stops the pipe entering the fitting far enough.
This means the teeth do not grip the pipe all the way round the circumference.
Thus, leaks.....
Personally I never use the inserts unless I am using compression fittings. (which I hardly ever do)
Take care out there....