Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.
Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

The AECB accepts no responsibility or liability for any errors or omissions in the content of this site. Views given in posts are not necessarily the views of the AECB.



Housing - Renovation: What Does FID stand for (ie m^3/hr FID) + help in choosing HR

Bottom of Page

1 to 17 of 17

  1.  
    • CommentAuthorGotanewlife
    • CommentTimeJul 4th 2013 edited
     
    Most of these wonderful extractor fans talk about extract rates in m^3/hr FID but could I find out what FID stands for, no I could not! Could someone please put me out of my misery.

    As to my apartment ventilation solution I have fiddle faddled around for months with various posts and much 'reading' but just go nowhere because I could not find a clear way forward, however, I HAVE to order the units within the next few days so I would be most grateful for your thoughts.

    Now what sort of extraction rate should I be aiming for in single occupancy bedrooms of about 40m^3? I have 2 such bedrooms. Noise is a big issue and so I was considering this unit:

    http://www.dealec.co.uk/acatalog/pdf/ventaxia/ventaxia.hr100r.pdf

    which, whilst I 'could' put in the ceiling void just about (suspended plasterboard ceiling under beam and block), I could also put in the adjacent utility room but what do you think about the runs from the unit to the furthest bedroom of 3.5m? The external wall is a nightmare, think solid granite blocks in a 550mm thick wall with the odd bit of loose stuff in the middle. So, could I join 2 units' external extract and vent together in order to make just 2 holes? Another thought was with a trickle of 49m^3/hr maybe I could get away with just one unit and split both the internal and the external pipes or extract from one bedroom and feed into another (the bedroom doors are just 1m apart in a corridor - kind of sneaky whole half apartment ventilation. The apartment is only 65m2 with 2.8m ceilings and I am fitting a Heatsava in the bathroom* with up to 45m^3/hr so do I need any more ventilation (the kitchen annex in the lounge will also have a super duper over hob extractor), with new windows and doors I am hoping for adequate air leakage.

    I don't want to go positive pressure ventilation and I do want HR for a variety of reasons too long to go through (again) here.

    *Yes I have read the recent Heatsava thread - will fit a cut out switch in case in-laws want a steamy shower! (actually I need it anyway as will be off most of the summer due to external temps of 30+ and internal temps 25+)
    • CommentAuthorbarney
    • CommentTimeJul 4th 2013
     
    FID = free inlet and discharge - ie, the fan performance without any ducting or louvres in place.

    Once you add system resistance, the performance changes,so you need to account for that as your design develops.

    Basically, work out your system resistance, and from the fan curve that gives you the system operating point - which you then adjust to get your design flow rates by means of dampers or variable speed drive - or you just live with the system performance and just let the fan stabilise in your particular duct system

    Regards

    Barney
  3.  
    Ta Barney, what this means to me is that HR100R with 77 m^3/hr FID is probably not too dissimilar to the Heatsava with 45 m^3/hr, which is stand alone - especially given the long runs, combined ducting and other gross things I am contemplating. Incidentally, the other choice would be a SRHR unit which I then box in (carefully splitting/ducting airflow) in order to reduce the noise.

    Looking for enlightenment.....
  4.  
    So according to VentAxia's take on UK regs I can use 0.3l/s/m^2 as a general rule of thumb for continous ventilation = 200m^3/hr for the whole apartment, or use a culmination of AC/H figures for each room. But, for example, the bedrooms at 3AC/H I get a volume of 75m^3, meaning a minimum of 225m^3/hr ventilation rate just for the bedroom - why is there such a huge difference in the scale of these figures? I am sure this is all std stuff for you but here is the link I used:

    http://www.vent-axia.com/files/Ventilation%20Design%20Guidelines%202.pdf
    • CommentAuthorEd Davies
    • CommentTimeJul 5th 2013
     
    Posted By: GotanewlifeUK regs
    Ain't no such thing - I think you're probably thinking of English regs.

    bedrooms at 3AC/H
    Sounds an awful lot to me. Values like 0.5 AC/h seem more reasonable.
    • CommentAuthorbarney
    • CommentTimeJul 5th 2013
     
    Start with the basics - for a single person in sleeping accomodation, you would want about 10 litres/second for a good air quality index

    That would give you 36000 litres of air an hour or about 36m3/hour - which is pretty close to your 40m3 bedrooms and come out at around 1ACH (which is generous as Ed points out) - you can afford to be on the lean side here as people are sedentary so a lower value of perhaps 6-8l/s

    The HR unit can do 77m3/hour FID, so you need to allow something for the ducting etc but the unit is in the right ballpark for two bedrooms.

    If you look at the fan curve on the manufactureres literature you should see that for increasing system pressure you get less volume flow, until the fan stagnates.

    Your duct sizing probably doesn't want to exceed 1Pa/m and your terminal louvres will probably exhibit about 10Pa pressure loss. Add that lot up for the worst favoured run and note the value.

    System resistance varies as the square of the air volume (Q). The resistance curve for any system is represented by a single curve. You can provide the points for the curve from System pressure(1)/System Pressure(2) = (Volume flow (1)/Volume flow(2) )^2 - re arrange for a selction of system pressures to find the flow rate and plot that on the graph of the fan curve - the intersection of the two curves is your operating point - ie what the system will deliver - or what that fan will deliver in your system.

    I've no time to crunch the numbers now, but as long as your ductwork runs aren't abnormally small or the runs particularly tortuous, then the 77m/3 hour unit will do the job with no problems. Put it remote from the bedrooms and have an inline attenuator on supply and extract if you want to reduce the duct acoustic transmission further (but be aware they also introduce resistance so you get less air).

    Personally, I would rethink the heatsava thingy in a bathroom, it's a pile of junk - golden rule for wet and naked is extract only - introduce the make up air elsewhere so it has time to warm before you introduce it to the bathroom occupant (lobby outside the bathroom for example, if mechanical with an undercut door or transfer grille) - or straight from an occupied area.

    You'll need significantly bigger air volumes if you want night operation to give a bit of cooling to the bedrooms

    Regards

    Barney
    •  
      CommentAuthordjh
    • CommentTimeJul 5th 2013
     
    Posted By: barneyStart with the basics - for a single person in sleeping accomodation, you would want about 10 litres/second for a good air quality index

    I'm not sure I understand that. The building regs values are for the whole house 5 l/s + 4 l/s for each person. So I suppose 9 l/s is close to 10 l/s for a single-person dwelling, but in Gotanewlife's situation with two single person bedrooms, surely the rate is 13 l/s for the whole dwelling?

    The floor area rate of 0.3 l/s for a 65 m² dwelling, OTOH, does work out to about 20 l/s I think. But both those calculations are for northern temperate regs and perhaps the sensible values are different in a warmer climate?

    Posted By: GotanewlifeNow what sort of extraction rate should I be aiming for in single occupancy bedrooms of about 40m^3?

    It's normal to push fresh air into bedrooms, not extract from them. Extraction is from wet areas like kitchens and bathrooms.
    • CommentAuthorEd Davies
    • CommentTimeJul 5th 2013
     
    Posted By: barney…and come out at around 1ACH (which is generous as Ed points out)
    1 AC/h for each of the bedrooms would be 0.5 AC/h for the whole flat if each bedroom was a quarter of the overall volume. So probably roughly consistent depending on what you're measuring the AC rate over. Perhaps I should have been clearer that I was thinking of typical overall AC rates and assuming inlets in the bedrooms and exhausts in the kitchen and bathroom.
    • CommentAuthorGotanewlife
    • CommentTimeJul 5th 2013 edited
     
    Thanks guys. Much better numbers Ed!! Yes djh supply into bedrooms, just me being inexact. During the winter my temps are a little colder than London, spring and autumn are warm versions of southern UK spring and autumn, summer is different but during the day all ventilation is off (via a cheap bespoke pre-programmed cut-out a previous post applies) and during the night all windows and doors are wide open plus, if available, extract only set to max.

    Barney, very, very helpful (I wouldn't have wanted you to run the numbers - too generous). For the whole apartment I have decided to run with a continuous ACH figure of 100m^3/hr or 27 l/s. I have decided not to get HR in the bathroom but to use a Vent Axia dMEV unit (the Lo Carbon Centra - 21m^3/hr and 1.4w at only 10.2dB!!). I have decided to go with HR for the rest of the ACH for many reasons largely unrelated to saving money or energy. I must provide in-laws with high quality air in the bedrooms (a previous thread on habitual window openers applies), with no single room HR fans approaching 10dB it has to be a ducted solution. You see I am making progress.... The previously linked HR100R doesn't quite cut it, especially as I must use 200x60 ridged or 100mm dia ducting for most of the internal supply and extract ducting. As far as I can find the next size up are the Xpelair Xcell 150 (£534 nude) and the Vent Axia HR200V (£515 nude) both moving well over 100m^3/hr at 100 Pa. Intriguingly, 2 x HR100Rs cost £450 and will manage the 80m^3 I am short probably (judging from your clues Barney) but it is a tight fit in my Utility Room and not easy to duct double the ducts on the house side.

    Of the 2 bigger Units the Xpelair comes spigoted for 60x200 ducting but it's 2 speed settings have to be adjusted at installation whereas for £90 more the HR200V can have a transformer giving the user 6 speeds available but comes with 150mm spigots. I guess the Xpelair is the choice of the 2 for me. The next size up is a big jump to £1100 ish and here the Xpelair do a Xcell200, ducted for 60x200 with summer bypass offering some cooling during the summer because it'll move perhaps 250m^3/hr in my set up alternatively at the same price point there is a Titon HRV 1.75plus giving summer mode, summer bypass and summer boost - also, though please check me here someone, it could well be fabulously better as at the 100Pa / 50m^3 point it consumes 26 watts, whereas the Xcell 300 appears to need 141 watts on minimum speed. Can that really be right? It still has the ducting issue though. Link to Titon and pic of my 'design' below:
    http://www.titon.co.uk/pages/products/ventilation-systems/mvhr/hrv-1.75-q-plus.php

    Edit: Looks like spigot adapters are no problem for any combination so not a decision criterion now and NO I can't go through the wall into the lounge
    • CommentAuthorGotanewlife
    • CommentTimeJul 5th 2013 edited
     
    OK found the Specific Fan Power figures and the Titon is under 0.5 whereas the Xcell 200 is over 3! Worried now - I usually don't follow up 'no price on the site' things but I called anyway as getting desperate and I got "It's not really my area but the price is £1055", might he have given me a duff cost for the Unit? Any other units at the £500 or £1000 price point worth a look at? I remember recently someone saying don't look at over 1.0 for SFP
    • CommentAuthorbarney
    • CommentTimeJul 5th 2013
     
    I wasn't suggesting slavish compliance with UK building regs for a non UK building (for minimum compliance let's not forget) - I was just using good engineering to be able to put a few numbers on the table for the OP to consider.

    Personally, I'd use the unit with a couple of in line attenuators to provide both supply and extract to the bedrooms (to mitigate the open window behaviour) and rig a set of controlls to allow extract only (or even revese the supply fan as well) for muggy summer evenings - it'll fit tidy in the smiley face room.

    For the lounge, I'd put supply into the lounge and take dirty extract from the kitchen and bathroom (ie at 50% per room of the supply air value).

    Job done - easy peasy, lemon squeey and with the HR 100 unit coming in on budget plus a bit for attenuators, you should have a high quality system for circa £1.2K)

    Regards

    Barney
    • CommentAuthorGotanewlife
    • CommentTimeJul 5th 2013 edited
     
    Well thanks barney - I guess I must have wasted 25 hours trying to understand all this and there you go one easy solution. Sarcasm aside.

    Posted By: barneysupply and extract to the bedrooms
    Do you mean one or 2 HR100s, if one, you mean T off so both supply and extract ducts go to both bedrooms?
    Posted By: barneyrig a set of controlls to allow extract only
    as these don't have summer bypass do you mean blanking off the external inlet and leaving the fan to pull against a dead head?
    Posted By: barneyrevese the supply fan as well
    I like that idea, just a bit of work twice a year but do you know that is always feasible with a HR Unit?

    Posted By: barneyFor the lounge, I'd put supply into the lounge and take dirty extract from the kitchen and bathroom
    you mean with another HR 100 unit - except I cannot run ducting in the lounge at all. I can extract and supply from the kitchen and shower-room but only through the wall into the storage room; the only mechanical option in the lounge is a Single Room through wall unit built into a cupboard sound proofed and with careful separation of flows and returns - feasible but with a bigger unit as per my diagram I wouldn't need to do that.

    You mention not going for a SFD of less than 1 but most fans don't quote this figure and the HR100 using its quoted Extract performance 66m^3/hr and 29W comes in at 1.5. I have more than £1.2k if I need it but I don't want high ongoing electricity usage.
    • CommentAuthorGotanewlife
    • CommentTimeJul 5th 2013 edited
     
    The HR 200 V seems to be edging ahead, looking at its power usage on its extract/supply vs Pressure curves. Ducting as per dia above, 150mm attenuators, supply T off at 150mm then then 100mm dia flexible ducting to bedrooms, with the 6 step transformer and hope I can turn the fan around for the summer (not essential but nice to have). That, plus the Lo Carbon Centra in the bathroom and BIG over hob extractor should do it. There will also be a cut out that says something like 'if internal temp is above 24 and external temp is above internal temp stop power'. All in circa £1k. Any better suggestions really welcome, within my rather awkward installation limitations! I especially would love to find a decent SFP ducted HR unit under £1000.
    • CommentAuthorbarney
    • CommentTimeJul 8th 2013
     
    1 x HR 100mto do both bedrooms - from the unit, through an attenuator, to each bedroom via a branch with a volume control damper at each inlet louvre for balancing.

    Ditto for extract, but you robably don't want the VCD

    Just switch off the supply fan in the summer evenings and have extract only with air inlet via leakage.

    You can just wire a reversing switch for the supply fan to give you extract - how efficient that is will depend on the fan type, but the objective is to move cool night air through the flat to give "coolth" to the structure.


    For the lounge, I'd use another HR 100 unit mounted in the store - you can duct the lounge air supply above the kitchen units, or use flat ducting above ceiling ( don't you have beam and block above, so I've assumed a suspended PB ceiling - if you get the hangers the right direction it should be a piece of cake).


    Specific fan power is basically a choice of what motor is used to drive the fans and what type of fanis used. I'd have a preference for backward curved centrifugal fans and DC motors - but there again, I'd probably buy an empty acoustic enclosure and a good Xflow heat exchanger and build the HR unit myself.

    Regards

    Barney
    • CommentAuthorGotanewlife
    • CommentTimeJul 8th 2013 edited
     
    <blockquote><cite>Posted By: Gotanewlife</cite>except I cannot run ducting in the lounge at all</blockquote> ie in the lounge ceiling, or in the kitchen ceiling or bathroom ceiling as beam and block - no possibility whatsoever.

    I have bought this one:

    http://www.fantronix.com/acatalog/Heat_Recovery_Unit_-_VUT-100_Mini.html

    £250 on t'net. it's not great as in its worst case SFP is 1.9 - ie a little worse than the smaller Vent Axia one. But the only other Unit with this type of configuration I could find with better performance is this one:

    http://www.solarcrest.co.uk/proddetail.asp?prod=HRV111

    which is outstanding with SFP from 0.54 to 1.14 but at £1190 and 234m^3/hr its like using a sledgehammer to crack a nut. Other than other dire examples above at I could find no other alternative.

    Edit - I made a mistake, I bought the VUE version which is only suitable for cold dry climates Canada etc, the VUT version isn't for sale as at 23 Dec 2013 but is expected to be for sale in the Ne Year - WARNING don't buy the Vents VUE 100 P Mini for a UK MVHR system unless it is for a hydroponics use.
    • CommentAuthorbarney
    • CommentTimeJul 8th 2013 edited
     
    OK - the fantronix unit isn't that dire - it might just scrape through current UK building regs and if you but a tree or two with the money you saved you could call it carbon offsetting anyway

    I still don't understand that beam and block issue though - given that from below it's castellated ? so you have packers and hangers and PB - or is it truly continental and is a hollow pot floor onto which a render and set finish is applied to form a truly solid ceiling ?

    Regards

    Barney
    • CommentAuthorGotanewlife
    • CommentTimeJul 8th 2013 edited
     
    Posted By: barneyor is it truly continental and is a hollow pot floor onto which a render and set finish is applied to form a truly solid ceiling ?
    Got it in one - concrete beams, hollow blocks dropped on top with base of block level with base of beam and rendered/plastered directly - same throughout my house it is just that in the lounge kitchen area I need all the height I can get whereas in the bedroom area there will be suspended plasterboard ceiling 120 lower as place is full of services for my kitchen above and the floor has previously been dug out a bit.

    Turns out I might have to make a little hole where the 2 supply 90 deg bends join the supply cieling grills as depth of 90 deg bend is greater than void by a bit. No big deal. What do you think about 50cms of attenuator flexible pipe to join the the house side supply/extract to the unit? And I guessed since no wet room being extracted and utility room, though unheated, is inside the house with fridge freezer in it and wood burner next to it, I would not need to worry about condensation in the short supply duct from outside, especially as I can have a straight section angles down to Unit and then a slight fall on the other straight section out of the house?

1 to 17 of 17

  1.  
Add your comments

    Username Password
  • Format comments as
 
Back to Discussions Top of Page
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press