Lagging ducts in a warm air system

Beenie

We have a warm air heating system at home.

A furnace wafts hot air around the house via metal ducts under the floor. Each room has 'registers' through which the warm air flows out. All well and good.

The problem is the insulation/lagging in the furnace room. It was installed by the previous owner and is a bit of a bodge. It looks like rock-wool style blanketing, covered over with thick black plastic sheet, all held together with string and those elastic things that people tie parcels to the back of their motorbikes with.Lovely.

I want to rip it all away and do a nice job of re-lagging but am not sure what to use. The problem is that this sort of system is not available now (popular in the 1960s but not much after that) and there's nothing on the market as far as I know that is similar. Lagging ordinary central heating pipes is standard and all DIY places stock polystyrene kits for that, but I've not seen anything for ducts that are about 12" square.

Any ideas?

MX5huggy

Firstly should you be doing anything with a 1960's warm air heating system apart form ripping it out and getting something more efficient.

Industrial/Commercial applications use a lot of square duct.

But I would look at Celotex or Kingspan board insulation you can cut this to size and stick it on with glue or tape. But look at the heat performance of the insulation and glue.

wallbash

Firstly should you be doing anything with a 1960's warm air heating system apart form ripping it out and getting something more efficient.

Care to back that statement up with costings??

WobblyDog

Depending on how large the furnace room is, and whether it needs heating itself, do the ducts in there actually need lagging?

My mum's got a hot-air heater in a large under-stairs cupboard, and the steel air ducts in there are un-insulated. The exhaust flue appears to be made from some kind of abestos, so that's something to watch out for.

On the subject of cost, the pilot light for the hot-air heater appears to use an astonishing 5kWh of gas per day during the summer, so I'm going to turn it off in March.

wallbash

On the subject of cost, the pilot light for the hot-air heater appears to use an astonishing 5kWh of gas per day during the summer, so I'm going to turn it off in March.

Our boiler also heats the water ( summer time) also when was the boiler last serviced?

5kWh of gas per day during the summer, seems a lot.
Our pilot light is small

WobblyDog

It has separate hot-air and hot-water burners (each with own pilot light) within the same casing.

The hot-water part seems to use about 10kWh per day. By turning off the hot-air pilot light during the summer, I determined that it used about 5kWh per day.

It does get serviced once a year, but I suspect the technician is more concerned with safety than running costs. The hot-air pilot light was quite large. I reduced it's size a bit using the adjusting screw, but I'm concerned that making it smaller will result in louder "whoomphs" when the main burner lights - they are already fairly dramatic compared to modern boilers.

r2015

WobblyDog wrote: »

It has separate hot-air and hot-water burners (each with own pilot light) within the same casing.

The hot-water part seems to use about 10kWh per day. By turning off the hot-air pilot light during the summer, I determined that it used about 5kWh per day.

It does get serviced once a year, but I suspect the technician is more concerned with safety than running costs. The hot-air pilot light was quite large. I reduced it's size a bit using the adjusting screw, but I'm concerned that making it smaller will result in louder "whoomphs" when the main burner lights - they are already fairly dramatic compared to modern boilers.

That seems like my system, 3 kWh for the hot water and 5 kWh for the heating.


I turn the pilot light for the heating off in the summer when I'm not using the heating.

We have a power shower using the heated hot water from the HWT and with cooking by gas use about 18 kWh of gas a day in the summer.


There is no way I would save on gas usage what it would cost to replace the heating so until SG says it cannot service it any more it stays.


Plus it is more responsive than radiators.


Also all my lagging is on the ducts that pass through the attic, elsewhere where there is no lagging on the ducts, it helps to heat the house.

Furts

Beenie wrote: »

.

The problem is the insulation/lagging in the furnace room. It looks like rock-wool style blanketing, covered over with thick black plastic sheet, all held together with string and those elastic things that people tie parcels to the back of their motorbikes with.Lovely.

I want to rip it all away and do a nice job of re-lagging. The problem is that this sort of system is not available now (popular in the 1960s but not much after that)

Any ideas?

I would be concerned that this could be brown asbestos - typical insulation from 1960s-1980s. Have you had the material tested? If not pause and think before ripping it out.

Beenie

We don't want to take it out as it's a really effective heating system. When you get back from holidays in the winter say, and the house is stone cold, you can get it up to heat within 10-15 mins with the air on full. That never happens with radiators.

The fuel used to be oil but was replaced by a gas furnace in 1993/4. That's when it was crudely lagged with what looks like rock wool blanket. I haven't had it checked but I'm pretty sure it's not asbestos.

wallbash

Beenie wrote: »

We don't want to take it out as it's a really effective heating system. When you get back from holidays in the winter say, and the house is stone cold, you can get it up to heat within 10-15 mins with the air on full. That never happens with radiators.

The fuel used to be oil but was replaced by a gas furnace in 1993/4. That's when it was crudely lagged with what looks like rock wool blanket. I haven't had it checked but I'm pretty sure it's not asbestos.

So am I.
Did have a sheet of 'white' material on the door to the hall , but got rid of that a couple of years ago

Ps Love my warm air.