MVHR design?

[marmic]

Hi all,  have been trawling around looking for MVHR design info to enable me to work it out myself with a view to buying unit and ducts etc and fitting - but struggling to find guidelines. Assume key points will be room volumes / positioning within rooms / duct volumes/lengths. (we are building a circa 100m2 single storey passivhaus). Hoping somone might have some pointers please? I'm about to look at in detail and need to make some decisons. Mostly exposed ducts - plant room for the unit itself. duct layout should be straightforward with primary straight runs through central hallway with branches off into rooms

 

I did approach a few companies at early stages some time back now wanting a conversation - but just received quotes (useful for cost plan but not requested!). Unfortunately they just give lump sums and can't say what they've allowed for in terms of design - but won't design until ordered, and for a fee! Seems like a rather cloak and dagger market!  And commisioning? Really necessary? Surely can't be that complicated!? We aren't going to buy something without due diligence and understanding what we are getting so finding it all very frustrasting / strange!!  Or failing a diy design and buying components option 2 is a supply and install company who will actually have a proper conversation and discuss reuirements in detail - hoping somebody has had some good experiences with a company that is more up front and can provide a recommendation please?

 

many thanks          

[JohnMo]

Start by reading building regs. That is always the starting point. Then read passivhaus house MVHR guidelines, they are different but relevant. You need to design based on building regs flow rates as a minimum. Room size is not really relevant it's usage is.

 

Two ducting design method. Branch or semi flexible from a plenum. Semi flexible is way easier to install, no room cross talk to consider.

 

Always look for the longest travel distance between flow in and out points. Depending on your layout coanda effect nozzle can be good.

 

Get a unit that is running at about 50 to 60% of is design rating in normal use.

 

Work out overall flow rates and room rates, the overall in flow will always equal out flow total.

 

A simple guide to flows attached 

[marmic]

thank you - will be getting my head into this saturday with plenty of coffee!