Quick U-value question

gutteruu

I had to lay 2 pipes across my garden for my oil boiler. Plumbers suggested nothing but "[URL="file:///C:/Users/baz/Downloads/Calpex%20Technical%20Catalogue.pdf"]CALPEX[/URL]" which was 30+ quid a metre. Instead I got a 4' duct, ran 2 x 1 inch pipes inside. I covered each pipe in ARMAFLEX (pipe) insulation, filled the whole duct with expanding foam and wrapped it in "ALUBUBBLE" insulation.

I would love to know how much better the insulation value of the mad expensive Calpex is, or even if it is. I'm being doubted so would love to throw back figures at them. My way worked out at 20% the cost.

I think each link has the u/r/k/etc-values listed.

Thanks

esox28

You seem to have done a top job there and wouldn't think heat loss between the two pipe installation would be calculated as much, but is there any chance ground water could ingress your ductwork?

The duo pipe suggested by your installer is water tight that's the difference.

gutteruu

Not completely water tight but as tight as is possible. I drilled holes along the 4' duct and filled until expanding foam was bulging out everywhere. I taped up the pipe insulation joints and alububble around the outside also. Bedded pipe in sand to make sure stones don't break through. I just can't get over the massive cost of Calpex. 32 euro per metre and 20 Euro Per fitting at each end. Took me 20 mins to make up 18 ish metres of this and I'm guessing its pretty much similar insulation wise. 650 euro for calpex, 110 for mine. I'm guessing I must be missing something.

MicktheMan

gutteruu wrote: »

Not completely water tight but as tight as is possible. I drilled holes along the 4' duct and filled until expanding foam was bulging out everywhere. I taped up the pipe insulation joints and alububble around the outside also. Bedded pipe in sand to make sure stones don't break through. I just can't get over the massive cost of Calpex. 32 euro per metre and 20 Euro Per fitting at each end. Took me 20 mins to make up 18 ish metres of this and I'm guessing its pretty much similar insulation wise. 650 euro for calpex, 110 for mine. I'm guessing I must be missing something.

Maybe a way to determine your "saving" is to measure (now, in one year, in five years) the temperature drop across the flow pipe between the boiler and the house, noting the general ground temperature as well. Then you will be able to compare / contrast with Calpex data.
You should also be able to work out and monitise the temperature drop in terms of oil wastage. Then you may see what you're missing (if anything). If you do this then please come back and tell us.

gutteruu

Don't know if I'd have the will to do it though. Any way to work it out from adding U-values of each?

esox28

The quoted heat loss of calpex over 100 mtrs is 1deg C.
should be easy enough to determine the hear loss through the temp drop of your installation.

You would have been better off not drilling holes to put 'expanding' foam in, but to use 90* bends up turned above ground inside boiler casing and termnated inside the building envelope to insure no water gets into duct.

Essentially what you've installed is a French drain, layer of sand, duct wrap, duct wirh holes...french drain.have you ever seen 2-3 year old expanding foam? It turns to sh#t.

Dont want to come across as been critical.

why could you not install boiler tight to the house?

gutteruu

esox28 wrote: »

Dont want to come across as been critical....why could you not install boiler tight to the house?

I'm happy for criticism. I just guessed how to do it during spur of the moment but I've been thinking about it since.

Fumes would be right under room vents and also in the way. I did use bends and brought it up through concrete slab at end to terminate inside boiler house. It was just connected underground at existing point to run into house below ground.

Only way I could get foam in was to drill holes as I figured foam would displace as much water as possible. I am guessing water would ingress either way especially with expansion and contraction of heat. I used foam to try stop water filling pipe more so than its insulation properties. But in hindsight you may be right.

galwaytt

I'm afraid esox is right: the expanding foam will rot when it gets damp. And once damp your insulation will be for nought: water conducts heat very well. ...