Heating estimate..your thoughts?

[Cecile]

We received the first of at least two estimates on the ducted heating. We were VERY clear that we required the higher R-value for the ducting, which is going under the house. Clearance is good (min 400mm). The estimate stated:

Ducting quoted is R1.0 as R1.5 will not fit under floor joists.(400mm R1.5 is equal in size
to a 500mm R1.0 , that is 18" in the old scale and you don't have the room for that)
Standards require only R.6 for underfloor installation in regional Victoria.

I'm a bit puzzled that he would sell to standard rather than try to source ducting at R1.5 that will fit. Does such a thing even exist?

Ted also asked about Electrostatic Filter to cater for asthma. These were quoted as a whopping $1300.00 extra. Maybe we asked for the wrong thing.

This is a reputable company that sells thousands of systems every year, so I'm not concerned about professionalism. We do however want to make our renovation to at least 5-star standard.

Over to you...thanks.

[johnc]

We are going through the same process replacing an existing underfloor system, we don't have 400mm clearance and the existing system touches the ground in several places as it is. We will have no choice other than to put in a ceiling vented system regardless of the duct size. From what I could work out for the size ducts to get the 1.5 rating you get thick ducts. Our old system they rated as a 1 the new when we go ahead will be a 6 without the age related leaks the old one has to the outside world. I suspect the old one if you take the leaks into account is six rated as well only you need a minus before the six which makes it pretty dreadful. Can't complain though it has chugged along for 30 years without a major breakdown and still runs without trouble.

[Wavenut]

Hi cecile,

how much was the estimate? Did you ask them to price a ceiling system as well?

[GraemeCook]

Good morning Cecile

Most common insulation materials - polyester, glass fibre, rockwool, etc - have an insulation value of about R=0.7 per inch. This means that insulation rated at R=1.0 should be about 36mm thick, and R=1.5 should be approximately 55mm thick.

Thus the external diameter of 400 mm duct should be approximately R=1.0 - 472mm and R=1.5 - 510mm. Though not ideal, the thicker should distort easily to fit into 500mm clearance.

Incidentally, 500mm R=1.0 duct would have an external diameter of about 572mm. Someone's been waffling....

Fair Winds

Graeme

[Cecile]

Hi cecile,

how much was the estimate? Did you ask them to price a ceiling system as well?

The first estimate was $3807 to 7 points using lower R-value ducts than what we requested, although I am not too sure where he has located them. There was a whole bunch of what he can't do, rather than what he CAN. We're not too interested in having the ducting in the roof space, unless the unit could be mounted high on an exterior wall. We didn't get an estimate of installing in the roof space (which is clean, well-insulated and accessible.

[krico]

What sort of heating are you going for? Gas or reverse cycle?

It says 400 MINIMUM but what size duct needs to under that? It may only need to be 6 or 8 inch as the quote was for 7 outlets so the maximum duct size should be no more than 14" or 350mm at the unit and then branching smaller. Besides, unless you are on rock it is not hard to dig under bearers etc to make duct fit, I do this quite regularly where space is limited and have to get duct through.

Krico

[Cecile]

What sort of heating are you going for? Gas or reverse cycle?

It says 400 MINIMUM but what size duct needs to under that? It may only need to be 6 or 8 inch as the quote was for 7 outlets so the maximum duct size should be no more than 14" or 350mm at the unit and then branching smaller. Besides, unless you are on rock it is not hard to dig under bearers etc to make duct fit, I do this quite regularly where space is limited and have to get duct through.

Krico

This is for gas ducted.

Interestingly, the second company who came agreed immediately that the R1.6 ducts would be fine with the available clearance. I am guessing that I'll go with the estimate that can fulfil what WE need, rather than what they want to sell us, unless it's ridiculously higher.

[Bloss]

I am a long time hayfever asthma sufferer - ditch the electrostatic filter - waste of money IMO. There are so many sources of dust and these are effective on a few and not all that much. A bigger problem is the reduced humidity - I added a humidifier to the last two systems and that really did help."

As to ducting - as you seem to have decided go with those who tell you what you can do - and when anyone says 'the standards say . . ." - tell 'em Bloss nags you endlessly that "minimum standards are not best practice" . . . and that ducting will fit fine.

And heating ducting in a ceiling is just dumb - so as you say don't do it.

[PeteV]

try rickard heating. 5221 6161

hope this helps!