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.




Ventilation: Ventilation for New Build

Bottom of Page

1 to 15 of 15

  1.  
    • CommentAuthorbardo
    • CommentTimeOct 22nd 2019
     
    Hi, I'm a first time house builder and looking to install moisture extractor fans from above a DIY kitchen cooker hood and in the bathroom (with bath and shower).

    The cooker and bathroom share the same party wall.

    Our walls are wide : 550mm (straw bales 450mm wide with another 100mm of lime / cladding/battens on the outside wall).

    Can anyone recommend a simple effective way of doing this Do we really need MVHR or just a simple extractor fan? Any brand/models?

    Thanks
    • CommentAuthortony
    • CommentTimeOct 22nd 2019
     
    Well, extract fans suck hot air out of the house wasting the energy in it. At the same time an exactly equivalent amount of cold outdoor air is sucked into the house through vents, gaps and cracks😢
    • CommentAuthorGreenPaddy
    • CommentTimeOct 23rd 2019
     
    Like Tony, I believe recovering heat (even better latent heat energy) is much smarter than chucking it all away, plus MVHR is constantly washing/freshening the rooms. Traditional extract fans just get switched off, as they're too noisy, leaving a very damp atmosphere.

    Try googling..."single room heat recovery"

    That will bring up various unit that are a bit like an extract fan, but have heat recovery built in. It should also bring up small MVHR units, which would involve some ducting (makes like Boulder and Quiet-vent 150) - a few hundred quid, rather than £1500 for the large units.

    See what you think, and maybe come back for more thoughts?
    • CommentAuthorjfb
    • CommentTimeOct 23rd 2019
     
    Whether or not to go for MVHR depends on how airtight you are planning to get the build. Anything under 3 ACH @50Pa (3 air changes per hour at 50 pascals) requires mechanical ventilation. Anything greater than 3 and MVHR is less useful (lower numbers are more airtight).

    Presumably in a straw bale house the render on the inside is the airtight layer. So long as you pay close attention to details of junctions between different materials, windows/walls, walls/roof, it is very possible to get a good air test result and get well below 3.
    • CommentAuthorCWatters
    • CommentTimeOct 23rd 2019 edited
     
    In my opinion it's all about control...

    If your house isn't air tight you end up with some unknown and uncontrollable amount of ventilation and a matching heat loss.

    If you build an air tight house you can/must control the ventilation by designing it in. You could specify adjustable trickle vents but with these you get limited control because ventilation depends on the wind. You also loose heat because air goes in some vents and out of others.

    MVHR is much better. Not only because air goes in and out via a heat exchanger recovering the heat but you can control which rooms get incoming fresh air and which rooms have extract vents (at the design stage).

    We opted for MVHR and was surprised to find we didn't need a separate extractor fan (or boost option on the MVHR) in the bathroom despite four of us using the shower. Your mileage may vary.

    We did fit an extractor fan over the hob but it's not used a lot.
    • CommentAuthorbardo
    • CommentTimeOct 23rd 2019
     
    Thanks all. We have gone for adjustable trickle vents in the windows despite the mentioned reasons. The calculated heat loss is around 3kw. What this will be with a vent hole in the floor for the woodfuel combi oven I don't know. I'll look into the single room MVHR as recommended and get back.



    Posted By: CWattersIn my opinion it's all about control...

    If your house isn't air tight you end up with some unknown and uncontrollable amount of ventilation and a matching heat loss.

    If you build an air tight house you can/must control the ventilation by designing it in. You could specify adjustable trickle vents but with these you get limited control because ventilation depends on the wind. You also loose heat because air goes in some vents and out of others.

    MVHR is much better. Not only because air goes in and out via a heat exchanger recovering the heat but you can control which rooms get incoming fresh air and which rooms have extract vents (at the design stage).

    We opted for MVHR and was surprised to find we didn't need a separate extractor fan (or boost option on the MVHR) in the bathroom despite four of us using the shower. Your mileage may vary.

    We did fit an extractor fan over the hob but it's not used a lot.
  7.  
    Posted By: bardoWe have gone for adjustable trickle vents in the windows despite the mentioned reasons. The calculated heat loss is around 3kW.

    3kW per what? hour? day? month? or a continuous 3kW loss?
    •  
      CommentAuthordjh
    • CommentTimeOct 23rd 2019 edited
     
    Posted By: Peter_in_Hungary
    Posted By: bardoWe have gone for adjustable trickle vents in the windows despite the mentioned reasons. The calculated heat loss is around 3kW.

    3kW per what? hour? day? month? or a continuous 3kW loss?

    Normally such figures, and the corresponding heat load figure, refer to the maximum rate of heat loss/supply needed to keep the house at a constant temperature at all times. The heat load will be greater if heating the house from cold. Normally, the maximum heat loss will be experienced when the outside temperature is at the minimum design temperature and the wind is blowing at maximum design speed.
    • CommentAuthorMike1
    • CommentTimeOct 23rd 2019
     
    Posted By: bardoThanks all. We have gone for adjustable trickle vents in the windows despite the mentioned reasons.

    Apart from the mentioned reasons, personally I'd also avoid trickle vents (at least in an urban situation) because of the noise they let through.
    • CommentAuthorowlman
    • CommentTimeOct 24th 2019
     
    Apologies bardo for hi-jacking your thread, but it's a similar theme.
    Does anyone know of a ceiling mounted single room MVHR unit? or, a wall mount for directly under the ceiling where the inlet/outlet has a top entry and can be angled to outside in the loft void?
    • CommentAuthorriboid007
    • CommentTimeJan 3rd 2020
     
    I have just installed MVHR (not moved in yet so not fully up to speed) and that will provide moisture control throughout the house. For the main kitchen though, I did not want to put the extraction vent above the cooker hob as i didnt want the extract ducting getting coated with grease (guaranteed) as there will be no future means of accessing it, so I am going to install a recirc cooker hood. I think there are 2 filters in it. I don't want to extract externally and that has been explained above eloquently.
    • CommentAuthorphiledge
    • CommentTimeJan 3rd 2020
     
    If your going down the recirc route then bare in mind that someone will need to clean the grease trap/mesh regularly. If you dont, youll just end up with a film of grease for few feet around where ever the extractor vents to. Weve got grease staining all over the wall/ceiling/cupboard tops around the recirc extractor vent. An external vent is on my to do list!!
    • CommentAuthortony
    • CommentTimeJan 3rd 2020
     
    I would vent the cooker hood to outside and only use it sparingly when necessary.
    •  
      CommentAuthordjh
    • CommentTimeJan 4th 2020
     
    It depends how you use your hob. We have a recirc hood, since we're PH, and don't have any problems with it. We clean it once a year or so, and I also fitted a filter to the MVHR extract terminal in the kitchen, since there was some dirt inside the duct at the first bend after the first year of running it. That filter gets washed or renewed every year or so as well. The hob is used every day but we never deep fry, although do stir fry a fair amount.
    • CommentAuthorSimon Still
    • CommentTimeJan 5th 2020 edited
     
    As I've said before on these threads - I can't recommend our Berbel cooker hood highly enough.

    Uses centrifugal force rather than just a metal mesh to remove the oil from the extracted air. Extra large, refillable carbon filter if using in recirculation mode or an insulated outlet that only opens when in use if extracting.

    Ours is recirculating with the kitchen MVHR extract relatively nearby. Very effective and easy to clean.

    After 4 years I've just changed the carbon pellets in the filter - since they're a widely available 4mm pellet used in other filtration systems that cost just £25 (they recommend changing about every 3 years). Most other recirc hoods recommend changing at least annually and a quick look at the Siemens site shows some of their replacement sets are over £100.

    When I changed the carbon there was negligible sign of grease that had got past the filters (whereas when I've cleaned the mesh filters of conventional cooker hoods theres a fair amount of grease coating the insides).

    Yes, they're super expensive but also very solidly made of heavy grade stainless steel and with very quiet motors.

1 to 15 of 15

  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