HRV Ducting

Espoo

Hi All
I'm new on boards so forgive me if I'm posting in wrong place. Trying to find my way around. Anyway I've installed Hrv ducting in the suspended ceiling of the ground floor of my house. Problem is the elbow bends that you fit the valves to can only accomodate 4 inch dia valves. Ideally they should be 5 inch. The ducting I have should be ok 204 x 60. So Do I somehow try to change things around so I can fit the 5 inch valves? or take a chance on the 4 inch? Ceiling is plastered so it will be messy to change.Runs are not too long. From 3 to 5 meters. Floor is 125 sq m with ceiling height of 2.55m. There will be 3 inlets and 3 outlets on the floor. Cheers Espoo

fclauson

Who designed out you system and specified the duct sizes, airflows, volumes etc - suggest you speak with them.

Otherwise go to either the MHRV supplier or the ducting supplier and ask their advice

a word of warning - I have seen a number of MHRV systems which fail to "V" i.e .the fail to ventalte at the right rate - thise leads to tell tell signs such as condensation on the windows when its cold etc - which probably means there is condensation forming in behind walls, roofs etc onto any cold surfaces.

Check out Part F of the planning regs to see what volumes you would need in each room

Espoo

Fclauson
Thanks for that. Yeah I will enquire from the company I'm buying the stuff off.
I see what you mean about the condensation. I will check out the regs. Better get it right as mistakes can be costly:(

Espoo

AMG86

One way around your 100/125 problem may be just to fit 4” valves and up the speed of the HRV system a little. The 204X60 should be adequate from an air volume point of view. However make sure air flows are measured as part of commissioning.

Espoo

Thanks AM
Yeah the 204 x 60 is plenty. Hrv crowd say it'll be grand. Can you advise me
on the flexi ducting? I understand this is good for sound insulation. But use too
much of it and it will push up costs to run the unit as it takes more effort to push the air through the flexi compared to rigid. How much of this stuff should I
use going to (fresh heated air) and from (exhaust air) the rooms? What about the incoming and outgoing ducts to the outside? I will have the unit in a small plant room/storage on first floor. I was thinking of using the flexi to get me in to the crawl space around room in roof, then use rigid ducting to outside. I was then going to insulate this rigid (along with the rest of the ducting going to/from rooms) when I get the guy in to insulate between the joists. He will blow the insulation in. Any suggestions appreciated? Sorry its a bit of a long winded one!

Troy McClure

fclauson wrote: »

a word of warning - I have seen a number of MHRV systems which fail to "V" i.e .the fail to ventalte at the right rate - thise leads to tell tell signs such as condensation on the windows when its cold etc - which probably means there is condensation forming in behind walls, roofs etc onto any cold surfaces.

Check out Part F of the planning regs to see what volumes you would need in each room

Can you expand a little on this and explain what this means exactly?

fclauson

Tony
as we build tighter and tighter we must make sure the building is ventilated correctly

if we fail to ventilate correctly then we will get condensation on cold internal surfaces - windows, mirrors etc - but more worrying is if you have failed to ventilate then areas inside you construction may get wet - cold timbers, cold steels, etc etc - and this then cause mould, rust and rot -

what worries me about this thread is that duct design etc is being done on the fly - as with everything - it should have been calculated and planned up front and confirmed that it would ventilate the building correctly. There are international standards and procedures for doing this.

Not doing so leaves too much to chance and problems for the future.

Read Part F - its very clear as to what is required - you might not agree with it - then consult a ventilation expert and put you case to building control but please at least understand what is the basic requirements