air conditioning rigid ductwork query

[goldpau]

hi all, have installed several ducting air conditioning systems and have always used insulated flexible ducting (as its always been hidden above a ceiling), now need to install ducting air conditioning system with rigid ductwork (it will be on display), have looked around and cant find any form of rigid ducting which is insulated - have spoken with ducting supplier and they have said they sell an insulation wrap which we can put over / around the ductwork but this is going to look crap as its on display - ive seen rigid ducting which is on display before and its not been wrapped with insulation - so what have they used? do they just use galvanised spiral ducting and not bother with any insulation?
please put me in the right direction, not used rigid ducting before, maybe its because i use insulated flexible ducting im expecting to use insulated rigid ducting - but cant find anyone that sells it - so maybe it doesnt need any insulation?
as usual your help is much appreciated!
cheers, paul

[RSTC]

Try coolduct from Kingspan http://www.koolduct.kingspan.com/koolduct/pdf/news_brunel_uni.pdf

L (http://www.koolduct.kingspan.com/koolduct/pdf/news_brunel_uni.pdf)indab also have a range I believe. http://www.lindab.co.uk/frameset/run_frame.asp?LangRef=12&Area=13&topID=3&ArticleID=18194&MenuID=515&Template=../templates/a_masterweb_standard.asp&ExpandID=3967&T=41&L2=1

Your local sheet metal company may also be able to make up something if you need something snazzy.

PAL preinsulated sheet ducting is also a nice finish http://www.pal-me.net/products.html (though it will be rectangular not spiral)

Do use insulation as the ducts will sweat, ruin feature ceilings, damage merchandise, stain furniture and the client will sue you.

[goldpau]

thanks for the links -

one of those just quoted me £175+vat for 1 x 3m length of 200mm rigid spiral insulated duct (that includes a 40% discount from list),

compare that to £20.00+vat my normal duct supplier quoted me for 1 x 3m length of 200mm rigid spiral un-insulated

over £150.00+vat to have 1x 3m length pre-insulated!!

seriously is this the going rate? must be a company out there whom is reasonable priced - i know most people dont like to share their suppliers details with others in the same trade but it would be really helpful if you could help me out or just confirm if this is the going price. cheers all

[al]

What about using fabric ducting instead?

al

[eggs]

I don't know how you price your jobs.............but as a quick rule of thumb.

I charge normal sized duct at a normal height (ie 100mm - 450mm up to about 3m to soffit) at £60 per linear metre......then £20/m for insulation.

By my reckoning that is that is £240 per length of insulated spiral installed.

If you want to work for free then go for it brother........or catch up.

Eggs

[goldpau]

eggs - youve misread my post,

im asking if anyone installs pre-insulated rigid ductwork (with the insulation internal so that on display is the galvanised part) and if so where they get it from,

im not even at the stage of pricing my job - i normally use pre-insulated flexible duct but on this occasion the duct will be on display so i want to see if there is a supplier out there whom sells internally insulated rigid ducts

[eggs]

In the past we have insulated our duct internally with armafex sheet and glue.

If the ductwork is on display within the conditioned space, ordinarily insulation is not necessary. If however the duct passes through an un heated/cooled space this is when sweating problems will occur.

Sorry for any misunderstanding earlier.

Eggs

[goldpau]

eggs

nice one, all of the ductwork will be in the space to be cooled / heated so nice to know it shouldnt need insulating.

cheers for the tip on the diy insulation though - there is no way i would have thought of that!

reminds me of a course i was on when someone was complaining about how long it took him to make a hole in a thick wall only a few days earlier - said his core bit wouldnt reach all the way through the wall so had to hammer and bolster it which took ages - should have seen his face when i asked why he simply didnt go outside and core drill the last bit from outside inwards - 'ive been doing this 20yrs and never thought of that' he said - couldnt stop laughing:D

[nike123]

Uninsulated duct will condense moisture on its surface if its temperature is below dew point of ambient air.

[TRASH101]

Further to Nikes post.........

You need to design your ductwork based on all reasonable conditions likely to be encountered for any part of the system.

i.e. if you have the potential of supply air temperature of say 4 celsius and the duct is surrounded by air of say 20 celsius and 60%RH an uninsulated duct is going to start dripping.

So in that case an increase in supply volume would allow a rise in supply air temp to get the same cooling "power".

[EuroairUK]

What about using fabric ducting instead?

al

This would definately be the way to go, Fabric ducting does not need insulating and comes with a coloured finish

[koolit5665]

Most manufacturers now include a feature (dip switch or field setting) on their ducted units to raise the off-coil temperature so that insulated ducting is not required.

We've used this a number of times and it works well!

Rick.

[Steven_AC]

depending on visual aspects of where it is to be installed, have a insulation company quote you to insulated your rigid ductwork.

[Gary]

Ductwork is not my thing, but maybe flexible inside the rigid?

[refcon32]

An insulation contractor would make an excellent finish on ductwork, which can even be painted, e.g black to disguise. Even have a aluminium cladding put on it.

Nev