Hi, planning for MVHR project

[woodman]

Hi All,

I've just about finished my 2nd retirement project, a 4 year renovation of a split level 70's bungalow in cold North Yorkshire. 

I've done everything myself, except where building control specifies otherwise, (2nd fix electrics,  boiler and woodburner commissioning. (Oh and I didn't plaster the ceilings))  this included converting an integral garage to living space, completely remodelling the interior (all interior walls were stud, fortunately) and most importantly, making it fuel efficient, as it's heated by oil, the cost of which can be highly volatile. 

I'm trying to make it as green as possible re energy efficiency, and  I'd like to move to a greener energy source in the future. A heatpump would be good if I can  further improve the building energy efficiency, however I'm in a conservation area so planning could be difficult.

 

 Efficiency improvements to date have been:

Wall cavity cleared of all builders rubble,

Cavity wall insulation (polybeads, as the external wall leaf is stone, undressed on the inner face),

cold bridging eliminated from all window reveals

double glazing panels replaced with planitherm throughout the house and conservatory

new conservatory roof, 1.0u glass

underfloor insulation in all areas with suspended floor

garage conversion compliant with Doc L

LED lighting throughout

original gravity flow central heating system replaced, underfloor pipes lagged

original boiler replaced with condensing oil boiler

Wiser heat control

 5kW woodburner

 increased loft insulation

 new external doors

 comprehensive draught proofing. 

 

The house is now warm,  heating costs are minimal,  but the price I have paid is poor internal air quality, so  MVHR is the next project,. Following extensive research, my plan is:

Loft mounted MVHR unit, Nuaire BOX95WH-1 (which I've obtained at a good price, summer bypass is not something to worry about in North Yorkshire!)   

Extraction  will be from 3 bathrooms and kitchen,  air will be supplied to living room, main bedroom and utility room.

 

I'm planning to use a 125mm branch system, as opposed to radial.

Reasons for this are:

1) Most of the property is single storey with good access to an unobstructed loft so installation is relatively straightforward

2) Increased  installation time is not important as I'm retired. 

3)  Larger duct size resulting in reduced airflow rate and noise( CSA of 125mm round duct =12271mm2 vs 6234 mm2 for twin 75mm OD semi rigid tube with 63mm ID) 

4) Allegedly, semi rigid radial duct bent at its minimum design radius can apparently distort and become internally ridged  after some time.  

5) Larger ducts should be easier to clean if necessary 

6) Cost, also semi rigid pipe appears to be available at a decent price only in large lengths eg 50 m or 100m. Using semi rigid, I'd need about 70m, so plenty of waste.

 

The  only downside as I see it,  is potential for increased cross-talk,  so I'm planning to include silencers between  vents. in addition to downstream of the MVHR unit.

 

I'd appreciate feedback on my assumptions/decisions, however this is probably posted in the wrong place for that.

Could I ask a moderator to advise if I should re-post/move this to the appropriate section?

thanks

b

 

 

[joth]

Welcome!

That's a great set of improvements! We're in a similar project right now, but starting out with the MVHR goal and everything else has followed from that... (EWI, floor insulation, air tightness improvements, etc).

Some comments / questions that come to mind -  not specific suggestions just list of things to think about and spur more ideas here really.

- Does the utility room have any wet appliances / laundry duties? If so extract maybe more appropriate there

- But if so, 2 supply feeds vs 5 extract sounds a very unbalanced system (even 3 supply vs 4 extract seems unusual, esp as the kitchen is generally "double" hence it's 3 vs 5). The air flow rate (and hence noise) might be extremely loud in those fresh air supply room. Normally the supply values outnumber extract valves (I have no idea if that's a "best practice", but it makes sense to me as the extract rooms tend to be places where a greater noise level could be more easily tolerated)

- how many bedrooms / reception rooms do you have in total? It would seem a mistake to not plan to supply fresh air into all of them (even if the install is phased)

- how long is it since the insulation was put in? I'm thinking you need a full year or two to determine if it's created any new damp issues (esp with respect to any rooms that you're not planning to put fresh air supply into, if any)

- do already you have numbers for the existing level of airtightness (in air changes / hr), and the total floor area of the house? Getting a blower door test done might be worthwhile.

 

Edited October 23, 2019 by joth

[woodman]

Hi, thanks for your thoughts- certainly some points I had not considered-

The utility does indeed have a washing M/C and condensor drier, maybe extraction would be useful here. I had not considered the issue of more extracts than supplies.

Layout is unusual. Two of the bedrooms (one with ensuite and one currently set up as a workshop) the utility, a further WC and the main entrance hall are in the lower level. Stairs connect to the upper level, where we have a large open plan kitchen diner, 2 bedrooms, 1 with ensuite, and a family bathroom plus landing/hall. Total floor area is around  133m2, upper is 91, lower is 42m2.

I had not considered adding vents to further bedrooms, as there are two of us living here, occupying one of the upstairs bedrooms.

However, I'm now thinking that adding a supply vent to a 2nd upstairs bedroom would be quick and easy, as would adding a supply to the upstairs landing, if only to reduce overall supply air velocity. Adding a supply duct to the downstairs bedroom would be more difficult,  the only way I can see this could be done would be to route a duct through the airing cupboard, which is on the upstairs landing, immediately above the downstairs bedroom. I'll give the idea some more thought.

The cavity insulation was done some 4 years ago. There is no evidence of any damp, so far so good....

I've never had an airtightness test done,  my method to identify draughts/infiltration has been to wait for a  cold day, close all windows, shut off the woodburner vents, then switch on all 5 extractors  (to be removed with MVHR) currently fitted- (ensuites/bathroom/coooker), wait for the pressure to drop internally, then hunt out individual air leaks using a wet finger!!  Very Heath Robinson, but it seems to work quite well. The entire rear of the lower level is underground, as the house is built into a slope, so no air leaks there! 

 

I have a question about silencers- I'm unsure whether they are better placed near the vent or nearer the MVHR unit- I suppose this depends on whether they absorb a set dB level, or a % of the total dB? Any guidance on this please?

My second question is about extract temperature:

I have a a woodburner which of course will produce high air temperates at ceiling level above it. This is a bungalow, so any heat escaping through the ceiling into the (well insulated) cold loft space is lost. The higher the air temp at ceiling level, (assuming loft remains at a constant temp)  the greater the heat loss, so is it a good idea to extract at this point (or close nearby to prevent potential overheating of the MVHR) to reduce the temp at ceiling height,  distribute this heat around the house via the MVHR and reduce heat loss through the ceiling? 

Or alternatively, taking into account the exchange losses in the MVHR, would this be wasting heat and  should I be extracting cool interior air to the MVHR?

[Jeremy Harris]

The issue regarding the number of extracts versus supplies is very important.  Extract rates will be higher per room very often, because building regs mandate the minimum extract level for kitchens, bathrooms, utility rooms and WCs, and these rates are significantly higher than the supply rates you would normally want in bedrooms, living rooms etc.  It's therefore best to have more supply vents that extract vents, to enable the system to be balanced more easily.  That way the flow rates through the supply terminals will be lower than that through the extract terminals, meaning noise will be lower.  A bit of noise on boost is normally acceptable in a bathroom or kitchen, but less so in a bedroom.

 

Silencers must be fitted as close to the MVHR as possible, before the main ductwork.

 

Unless the wood burner is a room-sealed model, with an external air supply, then fitting MVHR will really be a waste of time and money, as the extract rate provided by the wood burner when it's running will just overpower the MVHR fans in all probability.

[woodman]

Hi and thanks for the good info. What a great resource this site is. I've spent many educational hours reading  through the posts. 

I've now reconfigured my vents, and have 7 intake,  5 extract.  

However, in doing this, I have realised that the only way I can get a supply vent into bed 3 is to use a radial system- which raises more questions if I may:

1) I'm looking at BCP (quietvent) semi rigid 75mm. . The basic (green)  seems to be significantly cheaper than the std (blue) at £95 vs £144. Both appear to have the same CSA, I don't need the smaller radius capability of the blue, so that leaves the only difference as I see it, as the blue having an antibacterial coating whereas the green does not. Is bacterial growth an issue? If so, does it make sense to use green on the extract side only?

2) System noise is an important item for us, esp in bedrooms. I have read somewhere here that system balancing by flow adjustment at the ceiling valve is more likely to create noise vs adjustment at the manifold. It appears that the quiet vent manifold does not have the option to use restrictors, leaving ceiling vent adjustment as the only option. However, what is the opinion on using a clamp on the semi- rigid pipe just downstream of the manifold to balance the system? I'm thinking of something like a woodworkers clamp during balancing adjustments, replacing these with a slotted piece of wood for a permanent fix.  They could be removed for cleaning, A permanent set may result, but I guess this can be corrected for cleaning by lightly clamping at 90degs to the original clamp.

2)  Silencers. Looks like a potential minefield, as I cannot see any specs for attenuation performance. Recommendations welcomed. However, as I see The Ventilation Hub on ebay , who I think are actually Blauberg, (not sure if I'm allowed links on here) are selling a 150mm x 600mm silencer at a good price. As my  Nuaire XBOX 095 WH1 manual  recommends having a min straight 300mm  between the unit and any bends, I'm planning to mount the silencers vertically on the unit, then use flexi to connect to the duct work. Does anybody know of any downside to this? I was wondering if vibrations may be transmitted to the silencer from the unit.   

3) Using radial ducting, is it usual to put a silencer on the extract  duct? All my extract ducts are in rooms where some extract noise may be acceptable.

4) Woodburner- thanks for the guidance- my 5kW woodburner is not room sealed, however my logic is this: The wood burner air vents can be closed 100%, so when not in use, there should be virtually zero leakage through the stove.The woodburner is  likely to be in use for maybe 6 hours/evening, for 50 days/year.  That's 300/8760 hours/year when the MVRH won't work, which is acceptable for me.  At these times, the MVRH can however supply combustion air to the woodburner, an additional benefit. Can anybody see any other downside?

Thanks again for all the support this forum provides

 

Edited November 2, 2019 by woodman

[JFDIY]

As far as I'm aware there nothing to stop you having a beanch off in semi-rigid to the one room if that makes it easier to design?

 

I've just used blauberg components on my DIY design/install, they do a restrictor for inside the radial manifolds. Also the manifolds appear to be the same as the quiet vent ones. But about 20% cheaper than BPC once you set up a direct account, pipe is cheaper too.

 

 

[ProDave]

Re the wood burner.  I have a room sealed one and it has little or no impact on air leakage.  Even if you shut off the inlet air vent with yours the chimney will still draw air from the room.  I would see if there are options with your stove to fit a ducted air intake.

 

I used the radial system from BPC and my pipe was red in colour. I don't remember getting an option or what the different colours mean.  I ran two 75mm ducts to each vent to keep flow rate and noise down.

[dpmiller]

red is slightly more flexible than blue, the green stuff wasn't around when I called up to inspect and collect some stuff.

[woodman]

14 hours ago, JFDIY said:

As far as I'm aware there nothing to stop you having a beanch off in semi-rigid to the one room if that makes it easier to design?

 

I've just used blauberg components on my DIY design/install, they do a restrictor for inside the radial manifolds. Also the manifolds appear to be the same as the quiet vent ones. But about 20% cheaper than BPC once you set up a direct account, pipe is cheaper too.

 

 

That's interesting. I've just looked on the website, there are various option for business type. Did you set up a business account such as 'plumber', 'MVHR installer',   or a 'DIYer' account. I have a (now defunct) business name I could use if necesssary

[JFDIY]

Can't remember what I said my profession was, I needed a VAT number (used my parents farm), but to be honest I don't think you need much to get an account, I had managed to download the trade catalogue somehow before settling up the account so knew most of the prices beforehand.

 

Just had another look the price lists are linked in the start of the attached Link

[MJNewton]

Hi Woodman,

 

[Incidentally, this thread would probably sit better in the MVHR forum as it'd get more eyeballs on it there]

 

Quote

1) I'm looking at BCP (quietvent) semi rigid 75mm. . The basic (green)  seems to be significantly cheaper than the std (blue) at £95 vs £144. Both appear to have the same CSA, I don't need the smaller radius capability of the blue, so that leaves the only difference as I see it, as the blue having an antibacterial coating whereas the green does not. Is bacterial growth an issue? If so, does it make sense to use green on the extract side only?

 

It is interesting they are specifying different bend radiuses for their different ducting now as that was what I was going to comment on. I have used both Airflow (the red stuff) and Blauberg (green, which I suspect is what BPC are selling under the 'Quiet Vent' branding) and they are very different in performance when it comes to bends. With Airflow you can bend it right back on itself (not that you'd want to) and it keeps its shape however the Blauberg pipe kinks if you go too far with it. The Airflow stuff feels a much higher quality product and I'd suggest paying the premium for it for peace of mind as once it's in the house fabric it ain't coming out again!

 

Quote

2) System noise is an important item for us, esp in bedrooms. I have read somewhere here that system balancing by flow adjustment at the ceiling valve is more likely to create noise vs adjustment at the manifold. It appears that the quiet vent manifold does not have the option to use restrictors, leaving ceiling vent adjustment as the only option. However, what is the opinion on using a clamp on the semi- rigid pipe just downstream of the manifold to balance the system? I'm thinking of something like a woodworkers clamp during balancing adjustments, replacing these with a slotted piece of wood for a permanent fix.  They could be removed for cleaning, A permanent set may result, but I guess this can be corrected for cleaning by lightly clamping at 90degs to the original clamp.

 

That sounds like a bit of a bodge, and I think you'd struggle to crush as planned without damaging it. Far better IMHO would be to use the HB+ restrictor rings at the manifold end as whilst they are designed to fit in the HB+ manifold connectors they should, if trimmed down slightly, fit in any other connector between the pipe and the connector. Pricey for what they are but, as you have read, better at restricting flow from a noise perspective.

 

Quote

2)  Silencers. Looks like a potential minefield, as I cannot see any specs for attenuation performance. Recommendations welcomed. However, as I see The Ventilation Hub on ebay , who I think are actually Blauberg, (not sure if I'm allowed links on here) are selling a 150mm x 600mm silencer at a good price. As my  Nuaire XBOX 095 WH1 manual  recommends having a min straight 300mm  between the unit and any bends, I'm planning to mount the silencers vertically on the unit, then use flexi to connect to the duct work. Does anybody know of any downside to this? I was wondering if vibrations may be transmitted to the silencer from the unit.  

 

I wouldn't worry too much about specs as I beleive they would take some deep knowledge to meaningfully compare as I can't imagine you can sum up a silencer with a single figure as its performance will vary depending on frequency and any other properties of sound that I don't know anything about. I've got the Blauberg silencer but cannot comment on performance beyond saying I don't get noise from my terminals (I haven't tried it without in all honesty but for £30 for their 600mm one I thought it worthwhile).

 

Don't be afraid of cherry-picking different components from different manufacturers as they all should work together (some notable exception such as manifolds requiring matching connectors). I've got a Titon MVHR, Airflow ducting, Blauberg manifolds, connectors and silencer, Domus ceiling plenums and some others that are homemade (mine was a retrofit so above-ceiling access wasn't always possible), HB+ ceiling vents and HB+ restrictors. I tried to pick whatever I considered to be the 'best' aspects (function and value for money) from each range.

[woodman]

Hi, yes I'm cherry picking from different suppliers, I've been checking out minimum bend radii for various semi rigids, it seems the blaufast and the quiet vent red versions both specify a min rad of 150mm, the quietvent blue is 250. the re is no spec shown on the BPC site for the green basic duct.

 

Restrictors- thanks for the info,  I'd assumed incorrectly that the restrictors would not fit the quietvent manifold. I will comission the system then see if significant throttling is required at specific vents where I require low noise, and use restrictors if necessary.

If anybody is currently purchasing items, I've found that external bull nose vents are available at better prices on ebay, as is flexible insulated ducting, also on ebay. 

[JFDIY]

Picking and choosing definatly has merits, as does a bit of DIY creativity, just made a few 100mm vertical terminal housings for about £2.50 each, mainly because it was something I couldn't get easily ( @joe90 would be proud...). 

 

 

While a duct radius of 150mm might be quoted by blauberg, it'd kink in the corrugations I'd think - but not collapse, I've used it and have a load of off-cuts if you want me to post you a metre?

Edited November 4, 2019 by JFDIY

[woodman]

Hey thanks for your kind offer-I may take you up on it, I'm just considering a few other items first. 

A further question- as part of the picking and choosing activity, I will probably end up using manifolds, plenums and ducting from different manufacturers. I'm assuming I use sealing rings from the manufacturer of the duct, irrespective of the source of the end fitting I'm using?

 

[MJNewton]

I found it was better to match the sealing rings with the pipe as whilst the inner and outer dimensions might be the same the the rib spacing was wver so slightly different. There is also a difference between the sealing rings with the Airflow being a bit 'beefier'. 

 

If you want an Airflow offcut message me your address and I'll send a piece over. I've also got a spare 50m roll (or nearly 50m - not sure if I used any) which I need to move on at some point too. 

[woodman]

Thanks MJ,  good info.

I would be interested in your 50m roll of Airflow, however Wiltshire is a fair way from North Yorkshire.  If you can let me know what you want for it, I'll investigate courier costs. 

 

[MJNewton]

Between my brother and I we massively over-ordered (due mainly to a change in approach for both jobs midway!) and so I've already shipped a couple of rolls. It was only £12(?) via Parcelforce48 although they were right on the limit for dimensions and so crossed my fingers on both occasions that I wouldn't be pulled up on it! This roll has been opened though so might not go quite as small as when first delivered, but then it might be slightly short. 

 

I'll sort out some photos this weekend as I've been meaning to do something about it for a while. 

[woodman]

£12?  That's good! I've just been googling about, I assumed a pallet 1000 X 1200 x about 45. Weight about 25Kg. £57 is the best I could find.  Maybe I'm overestimating the size/weight

I wouldn't worry about photos, as long as there is nothing nesting/living/decomposing in it, I'd be interested.

 

[MJNewton]

Yeah it's quite remarkable. You can purchase Parcelforce services (collection or drop-off at the Post Office) via Paypal (this link) with a massive discount. For £11.99 you get the 48hr delivery service with insurance up to £100 (you can pay a bit more for extra). Max 30kg, length 1.5m and length+girth 3m. A coiled 50m duct is right on the limit for the length+girth dimension (slightly over if you were strict about measuring it). I know the weight is less than 30kg; not exactly sure by how much but it's not that heavy to lift - just awkward!

 

I'll dig it out at the weekend, check the condition etc, assess the feasibility of coiling it up tight again (it is in a 'resting' coiled state at the moment which would be too big to ship!) and work out whether I used any of the 50m or not. Will send you a message once done and we can take it from there!

Edited November 5, 2019 by MJNewton

[SteamyTea]

When it comes to shifting parcels, I use Parcel2Go, always amazed how cheap it can be to send stuff.

[woodman]

Hi MJ, did you have any success with the ducting over the weekend?

[MJNewton]

I did! ish... 

 

The ducting is the full 50m and still has the end caps in place, however there are a some scuffs and scrapes and it's picked up some dust/dirt on the outside in places where the wind has blown through. The biggest concern though is that I think I may have misunderstood Parcelforce's dimension limits as the 3m limit is for length+girth combined whereas I must've previusouly assumed it was just the girth (with length having its own 1.5m limit)! The coil is roughly 1m in diameter and 53cm high hence why I thought the 1+1+.53+.53=3.06m was pushing it. Perhaps they don't mind too much if it's still able to be handled (it's a one-man lift at around 17kg) and they've taken two previously without issue.

 

Given its condition and being more keen for space than excess ducting I'd be happy to offer it at half-price (so, £80 + £12.99 postage) if it's of interest otherwise I might just stick it on eBay as collection only the that avoids the risk of Parcelforce demanding excess fees if they decide it is over limit with this one! 

 

[woodman]

Hi thanks for your reply,  firstly I must say the turtle in the background brings back memories - my child had one exactly the same- but quite a few years ago! 

Yes.I'd be interested at £80 plus 12:99 delivery, if you can manage to get it shipped at that price. Blauberg are selling their equivalent antibacterial at £79.49 so it's worth a little extra (the shipping cost that is, not the 61p!) to get the increased flexibility of the red airflow.

If the shipping cost turns out to be significantly greater, then it may be better, as you say, to put it on ebay, buyer collection. 

Is it possible to confirm the shipping costs, then assuming you are able to work your magic on ParcelForce, how would you prefer me to pay for it?

cheers

Bryan

 

[MJNewton]

Unfortunately I think we'll only know what Parcelforce think once it's on its way - presumably they must have some sort of revenue protection process at the hub to check people are paying the right amounts? I don't think the drivers do any checks on collection. I've sent two previously and they seemed more interested in what it was than how big! 

 

Bank transfer would probably be easiest for me if that'd suit? I'm away with work for a couple of days but can get it wrapped up ready to go at the end of the week if you want to proceed. 

 

 

[MJNewton]

P.S. Not wanting to tempt you away but that Blauberg price seems pretty good, and would be 'pristine' unlike mine? Remember that you should be avoiding sharp bends anyway; not so much for kinkiness (matron) but more the impact on airflow.