Heat Recovery Ventilation in flat... the story...

[orionis]

Where to start...


About 9 months ago, we finally purchased our first, very nice ground floor, 2 bedroom flat. Within days (mid Feb) we found that this place really need some sort of ventilation as there was way too much condensation, so there it was: replaced bathroom fan (100mm) for more economical and more powerful, same with kitchen (and discovered that there was same cheapo fan 100mm)... Not much difference. Under cut door for better air flow. Not much change. Checked for any leaks. No leaks. Air bricks? Yes, biggest I have seeing in both bedrooms. They are always fully open thus making them really cold... But RH is still around 70% in the morning.

Next upgrade: we went for dehumidifier... It will extract about 2L of water in 4h. and drop RH to 55%, but... 3 settings where lowest is 350W and highest 850W measured at the plug, is no go for a long run.

Then it got me thinking: If this place is so tight, why not to fit properly functioning ventilation with heat recovery because to waste heat from kitchen and bathroom is plainly stupid.
So, I spent next to nearly 2 weeks researching trough various places for my ultimate MVHR. The options are varied but there it is one common point in all of them: PRICE. there is virtually nothing below £600 with some sort of quality build... Ok, they will tell you about 70-85% efficiency but with AC motors build in them. Basically very juicy and suitable for whole house application. What about flats...?

Then 2 items caught my attention: VUE-100-P-Mini @ £199 and HR-100-RS @£220. After research on various web pages i decided to get VUE-100-P-mini. What a disaster. Unit itself is great and very good quality but with wrong description. VUE-100-P-mini has Energy Recovery Paper Core and NOT Plastic/Aluminium Heat Only Recovery core. Description will tell everyone that you can connect unit to kitchen and bathroom but original manual on manufacturer page will tell you that this unit is not suitable for such configuration... All this I found after ordering and receiving unit at home and only after spotting lack of drain on casing... Unit going back to seller. I hope there will be no problems with it.

Next is HR-100-RS (bottom access), there are 2 companies having the same unit just different name Vent-Axia and Swiftair, but basically this is the same unit. So, unit received within 24h from ordering, very good. Smaller box than VUE and the unit is about half size of it. First impression: how this unit suppose to ventilate up to 30m of 100mm duct?? Never mind, lets open it.
You know, there are times that you just want to throw things around or shoot that person who design such a thing... Motor not fixed anywhere, gaskets sitting half way or is rolled off not sealing anything, core... CORE is just a piece of thin plastic sheets squeezed in between and gaps between sheets for around 4-6mm... this is for 100mm duct but if you look inside there is fan window about 30mm x 60mm inside of that round duct... I just wanted cry.

I've lost 1 week for it. Now, I have a problem with either keeping HR-100-RS in my cupboard and forcing to work and than replacing soon after I will get all the bits and build one off for myself, even knowing that it's just piece of.... or send back both units first thing on Mon. I'm working with big industrial Air Handling Units, but seeing this is just a shock for me.

 

[SimonH2]

Do report back what you decide/find.

Currently considering what to do in g/fs house - it's a 60's ex-council house and always seems quite damp (windows often running, some mould in places). I borrowed a dehumidifier (350W IIRC) from a friend and it sucked a lot of moisture out - but it's not really a long term option (and it's noisy).

I've been toying with making an MVHR unit to go in the attic - bathroom can draw through ceiling, and there's an easy route to put a duct down to the kitchen. An idea I saw some time ago was to get a load of the corrugated plastic that's used for packing and also for cheap windows - the extruded stuff where if you look down the end it's effectively a load of square channels. Stack a load of these together with spacers - so one flow can go down the channels, and the other flow can go up the gap between the sheets. Add some lagging (encase in "seconds" Kingspan ?), a couple of fans and some ducting and Robert's your mother's brother.

Of course there's a long list of other jobs to do first


Bit more on my thinking about design.
One flow must go along the channels. The other can be crossflow, but if it's made long then by feeding the air in at one end of the long side and drawing out out the other end of the opposite long side, it should be possible to make it mixed flow - with a mostly counter-flow element.

Also, whether to add a heater element. If I fit a thermal store (also on my list), then a low temperature loop round a heater panel would probably work fairly well - with it's own pump and TMV. Why do I having images of the old cartoons where cash registers go "kerching" and flags pop up with "$" signs on them

 

[orionis]

Hi SimonH2

After another set of thinkings, I decided to stay with VUE-100-P-MINI, as it was small and its quality was good. Bathroom and kitchen will have separate fans as connecting bathroom humid air may not be such a good idea, same with kitchen's oils... The other unit was send away. I just hope they will accept it without any problems.

Purchased from M Mart nice 1500W rotary drill made by Clarkie... It is just not my day, or someone/something is just trolling me. Didn't checked for about 10 days, stupid me. When it came to drill, it is spinning drill bit anti clockwise and sparking from commutator like Christmas lights. WTF?! Called first thing in the morning Customer Support and was told that they need to do a next day pick-up (and wait for them between 9-5pm) or go to the shop, and leave it there. Then wait "up to" 12days!!!?? for assessment and repair or replacement... This is just what I need.

...and I got my 107mm core cutter today...

...and I moved my banking today officially... and of course they forgot to send those stupid card readers... so I cannot do anything on-line.

...anyway more time to plan things: cannot decide whether to put inlets (stale air) in bedroom and outlet (fresh air) in main corridor or all the way around. If I have outlet in bedroom that there is chance to blow colder air into the room, but If there will be inlet to suck stale air from bedroom, outlet (with fresh air) will be in hallway. Of course, all doors need to have proper ventilation ability...

Making MVHR is not that complicated. I've found that the biggest problem was casing and correct fans. But in the end, you can buy almost anything from China. and making your own wouldn't be a problem.

As for square ducting... It's very restrictive and noisy. You need a strong fan. If you want to do some sort of heat exchanger then you need very thin sandwich (thinner material = usually better heat transfer) for those two separate streams...

 

[David937]

Did you also consider the standalone heat exchanger from Vent Axia? You then choose what supply and extract fans to use from the Vent Axia Range.

I already have an ACM in-line fan for the bathroom, I've been considering adding another supply fan + the heat exchanger at some point in the future but it is pricey!


http://www.vent-axia.com/range/heat-exchange-unit.html

 

[orionis]

Hi David937,

Not really, firstly: this unit has 200mm spigots (twice what I need) and I have a very limited space, so no go there... secondly: after seeing HR-100-RS from vent-axia and its quality (or more like lack of it), I don't want anything from them. When all bits are patched up like it was designed by kid with no knowledge about anything, you just cannot force yourself to buy something from company like that. Don't take me wrong, they may be good with bathroom fans, but HR-100-RS made me cry...

As I said previously, no space, my unit must be all in. But, If I was to do something like that, I would choose other unit, something like this one http://fantronix.com/acatalog/Passive-Heat-Recovery-Ventilation-Unit.html

It's 90% efficiency (not 70% vent-axia), of course everyone is counting efficiency at 0m/s where unit has its max efficiency), has drains on both sides and is probably much better quality... And is cheaper!

But, it's a bit bigger than my VUE. I've changed original design to accommodate this unit, so no direct bathroom and kitchen connections to ERV, they will have separate extracts. (I don't think you want to have oil on your heat exchange core). Bedroom feed in with fresh air, main extract in hallway (to suck up all crap from whole flat, probably 2-3 inlets to balance out outlets from bedrooms & living, otherwise it will be noisy).

Still waiting for my drill, only after heated conversation, they agreed to send new replacement at the beginning of this week. We will see...

 

[SimonH2]

It's 90% efficiency (not 70% vent-axia)

Take that with a pinch of salt - it's "up to" 90%. It's the same crossflow design as the Vent Axia, so I'd not expect to see significant differences in efficiency other than due to the size of the HE core. Also, it's still just the HE core, so you need to add two fans before it'll work.

I've changed original design to accommodate this unit, so no direct bathroom and kitchen connections to ERV, they will have separate extracts. (I don't think you want to have oil on your heat exchange core).

The filters are (in part) to deal with any "not air or water vapour" that goes up the pipe. I noticed while I was looking around that someone (could have been Vent Axia) does a suction terminal with built in filter.

Personally I;d suggest you reconsider the bathroom and kitchen. They are two large sources of both heat and moisture - so not including them in the system will considerably reduce the value of it. But, just having the system running for the rest fo the flat will make a big difference - at least damp from the kitchen and bathroom won't make everywhere else damp.

 

[orionis]

Take that with a pinch of salt - it's "up to" 90%. It's the same crossflow design as the Vent Axia, so I'd not expect to see significant differences in efficiency other than due to the size of the HE core. Also, it's still just the HE core, so you need to add two fans before it'll work.

Hehehehe... This apply to almost everything: broadband "up to" 150MBit, mobile contract for "only" £4.99 (and will be £14.99 after 3 months, but they will never tell you that, and you have a 2-year contract ) Efficiency of the core is only part of the story, there is also efficiency of motors being used, type of insulation, length of ducting, size of it... etc etc. Best way to measure it is in real terms like what is in and out temps, how much motors actually take from grid, what is temp at the inlets/outlets. That way what goes in and out in real Watts, Amps, Volts. As you pointed out, this "90%" is most likely at 0m/s, so not "real" efficiency.

This also applies to things like an efficiency rating A,B,C,D... "My fridge is A+++ rating, so must be better than yours!"... "YES, BUT... MY fridge takes 150KWh per year and is D and it cost me £150, and yours does with 380KWh and it cost £800, so who is paying more?"... Do you know, where I'm coming from? It doesn't matter what efficiency you want, it matters how much money you are willing to spend or keep spending. My unit is only 70% efficiency, but cost me £199 and it will take max of 56W (I will check that after installation). Or I can take separate unit for £399+fans £75x2 and have a 90% for twice more... but no space for it, so next unit is in region of £600 (3 times more).


But... I still think that was better unit than vent-axia, especially quality wise and price.

The filters are (in part) to deal with any "not air or water vapour" that goes up the pipe. I noticed while I was looking around that someone (could have been Vent Axia) does a suction terminal with built in filter.

My night job is to work with big air handling units, where they are mounted mostly on the roof. I know this from experience, once filter gets oil, forget about: the air will always go trough easiest way, so it will bypass it in any possible way. Once, in the core... Lets say, it will be a b....ds to get out. Those plastic cores are fragile, we have alu or brass cores, so we can even jet wash it, but here... only chemicals and mild ones. And I forgot great one: once filters gets heavy, you may burn out motor or if you are lucky, just cave in filter... so maintenance is always important with AHU (Air Handling Unit).
I will try to get photo of one of our extracts which is dealing with oils from kitchen, than you will know what I'm talking about. Not nice. It has a drain for those oils (never worked) and it has to be clean out every month. Of course, this is extreme, but still possible, we don't know where your inlet(extract) will be positioned and how much cooking (oils) we will have to deal with.
Those filter you have mentioned, are only to stop particles (and rather big ones) to enter the core. Our extract have whole systems to filter oils and it still goes past them...

Personally I;d suggest you reconsider the bathroom and kitchen. They are two large sources of both heat and moisture - so not including them in the system will considerably reduce the value of it. But, just having the system running for the rest fo the flat will make a big difference - at least damp from the kitchen and bathroom won't make everywhere else damp.

YES and no. They are good sources of heat but for short term, don't forget ERV is working 24/7 (this is the power of HRV/ERV), so intermittent fan actually helps in keeping constant temperature in your place. Eg.: if your kitchen hits up 5deg more and you pump this 5 deg (centigrade) in all rooms, you start sweating... heat will radiate, no worries. To utilize most of it, you would have to have central system connected to each room, measuring temperatures/humidity everywhere and acting according to situation there. This is part of Building Control System (BMS). Too expensive for what it gains in the house, unless (like me) you want to play with it

Ok, while I am on attacking vent-axia, if you look at the terminating via roof slope... Geez, if you have a possibility of NOT terminating there, you MUST ALWAYS ENSURE you will do it. Why? Do you really want to have problems with water penetrating your roof? Everywhere, it's being advised not to, yet vent axia shows you that you have to.
In domestic environment, heating battery can be done via water supply off your boiler and not via 2kW electric heater (different story, when you have "unlimited" electricity in industrial/commercial building). And which one will be more "efficient"? Probably electric, but gas is 3 times cheaper.
This unit clearly being design for commercial/industrial environment, so I would just let it go, if I wore you. Unless you want to deal with shortcomings very soon... Or you have load of space to waste. Separate filter cassette, separate motor fans "minimum distance of 1 metre is required between heat exchange unit and the in-line fans" (it says a lot), massive ducting...

It' not about environment or "save the specie" thingy... Never was. It's ALWAYS about money. ALWAYS. If fuel was cheap, no one would give a cr...p about environment or efficiency, just "turn that knob up for me, will you?". You want 6.0L engine in your car? Why not?!

I do apologise if I sounded a bit pathetic but as I'm getting older I'm getting more frustrated with world around us and us as I species. Long story.

 

[SimonH2]

Out of interest, what sort of dimensions are the heat exchanger core in your unit ? And how many internal surfaces ?

Called in at a local signmaker yesterday, and blagged a (small) pile of Correx offcuts - I can get more if I go back every few weeks. Just trying to guess how big to make it - length and width are constrained by the size of the offcuts, but I can go as thick as I can get sheets for.

 

[Plantoid]

Hope to be going the MVHR route myself with a made in UK company not too far from here called NU - AIRE
They were recommended by an Aussie who plays with installing PV panels in the local area ,. he has one of their units in his home

Left an email on their website WED afternoon , though think I'd have done better ringing one of the numbers on their website.

On the face of things the units seem ideal for my damp bungalow needs , once I get the hob extractor problem sorted ( hopefully tomorrow ).

I'll keep you guys and gals informed of my progress , for it seems lots of us have been looking for a reasonably priced MVHR system manufactured here in the UK .

 

[gotanewlife]

Hi guys my first post. FYI the Vents VUE 100 P Mini is designed for hydroponics and cold dry climates (like the Ukraine where it is made!!) because it transfers water vapour from the extract back into the supply air streams (as covered above). I fell for that one too!!!!!! However, the 100 P VUT model will shortly available from Fantronix (and their other outlets etc) and the VUT doesn't have a paper heat exchanger and does have a condensate drain. This fan is outstanding IMO because it has a SFP of under 2, some of the fans mentioned above are in the dire 3+ regions, a reasonable efficiency (though I agree with the caveats above). It also has frost protection with a temp limit that is user definable from +30 deg to -30 deg, meaning it can be set as a summer bypass (turns of supply fan). The next nearest void mountable unit costs £900 (that's the Nu-air one mentioned above - with a SFP well under one it is superb but 3x the price!). So at the £300 is price point there is literally nothing remotely comparable, period. It is a no-frills unit but is well made as well. None of the single room ducted fans are really up to a 70m2+ flat and all of the alternatives cupboard shaped units will cost more because they are over sized for the small flat unit. Hope this helps. BTW the sellers of the VUE model should all be shot for not describing correctly what the unit should be used for - though they don't mis-describe it either so not illegal, just amoral!!!!!

 

[SimonH2]

BTW the sellers of the VUE model should all be shot for not describing correctly what the unit should be used for - though they don't mis-describe it either so not illegal, just amoral!!!!!

If they are failing to highlight a feature which makes the unit unsuitable for use in a manner that just about all other units are designed to be used, and as people would expect it to be used, then that is misdescribing it.

Not necessarily a good analogy, but if someone sells a claw hammer that the manufacturer says is explicitly not suitable for pulling nails out at all, and doesn't mention that fact - then they are misdescribing it by not mentioning that it isn't suitable to be used for a function most people would expect a claw hammer to be useable for.
You can be dishonest by omission.

But then, never put down to malice what can be explained by incompetence.

 

[gotanewlife]

We'll see if they agree with you: I am in discussion! They have agree the unit is for 'overseas' and 'hydroponics' but not yet agreed to publish any review I have written or to amend their description - I'll not this one go.....So silly because the VUT is really unique at present. BTW, if you need bigger flow rates but not too big and you don't intend to make it work at max with 'orrible pipe runs, then the Brookvent 2.1 (repeat 2.1, check 100% that it is the 2.1 ver) is the bees knees. If anyone is interested I'll explain why.

 

[SimonH2]

If anyone is interested I'll explain why.

Well go on then

 

[gotanewlife]

Well I meant if someone needed advice/was thinking of buying something like this I would put some effort into helping them - however, for general info below is a quick and dirty paste from the Green Building Forum:

I Posted this: I have just bought the Brookvent 1.2. I am no expert but I did put in about 3 full days of work trying to understand what all the various units had to offer because of 'the usual crxp documentation' ie non-std spec descriptors, missing data, etc etc followed by speaking with sales staff who knew less about their product than me, and nothing about the market. Brookvent were great on the phone and had good documentation and the unit had full user control over fan speeds across all settings independently and built-in humidity boost (an expensive extra for most units). Before buying one you need to check the spec against your requirements carefully as not the most powerful unit up against any pressure. General suggestion: For those all important performance curves, print them off as big as you can (use screen capture if req), then roughly sketch out all the units' curves you are interested in on one graph - the results will be most illuminating and tells you alot about what each mftr is trying to achieve! Of course you'll have to play with some units.

I am a DIYer but later in the same thread a 'pro' wrote:

The Brookvent Aircycle 1.2 is my current 'best buy' recommendation. Low cost, good efficiency and low SFP. Inbuilt humidity control is a major plus. It is also one of the most compact units on the market. There are more efficient and lower power units out there but they are much more expensive and some of the units are physically too large. I have approx. 100 Aircycle 1.2 units specified across 4 developments at present.

 

[ban-all-sheds]

Do not buy anything from Twistfix - their employees are all cheating, lying thieves, they steal from others as part of their business practices and their products are rubbish.