It is in the garage. Right in the corner. 

thanks for the replies guys, esp Aredwood.

Hammerer:

 

cadman:

 

In mild climates such as ours lagging pipes is not beneficial where they're not in use for long periods.

 

 

Insulating hot water pipes is always beneficial so I presume that you mean there may not be a positive financial return.

 

But even in the scenario "where they're not in use for long periods" - where the standing water in the pipes has time to cool down close to the environmental temperature - that does not mean there is no positive financial return. You would have to know the usage profile, the water temperatures, the pipe characterstics (length, diameter, material) and environmental factors (temperature, underground, in concrete, and so on).

 

In the absence of sufficient detail, the more sensible decision is to insulate the pipes. This is also recommended by BRANZ and the building code, even for hot water vent pipes.

 

It's not always beneficial - that was the exact point I was making. In the typical usage profile of a domestic installation and taking into consideration the volume of water in the pipes affected it's just not regardless of what BRANZ suggest. This is because despite the fact that though insulation slows heat loss through the pipe wall to the atmosphere the actual application of insulation to a pipe also increases surface area which on small diameter pipes can be a substantial increase thereby negating the value (W/m²) unlike the situation of insulating volume larger bodies where the surface area is largely unaffected by the addition of insulation. For this reason even reasonably large hot water pipes in manufacturing are rarely insulated in areas other than that for personnel protection.

If there's no financial benefit then what other benefit is there that is worth considering?

gzt: Warmer water at the tap in cold weather.

Only if there's a real measurable cost benefit too - which there isn't.

cadman:

 

gzt: Warmer water at the tap in cold weather.

 

Only if there's a real measurable cost benefit too - which there isn't.

 

Means you will be mixing in more cold with it, so using less hot water, so yes benifit in cold weather.

 Except it just doesn't unless the hot water is in near constant use. There is little convection in a small diameter pipe and little thermal mass so the water still goes cold in a relatively short space of time, insulated or not.

cadman:

 

Hammerer:

 

cadman:

 

In mild climates such as ours lagging pipes is not beneficial where they're not in use for long periods.

 

 

Insulating hot water pipes is always beneficial so I presume that you mean there may not be a positive financial return.

 

But even in the scenario "where they're not in use for long periods" - where the standing water in the pipes has time to cool down close to the environmental temperature - that does not mean there is no positive financial return. You would have to know the usage profile, the water temperatures, the pipe characterstics (length, diameter, material) and environmental factors (temperature, underground, in concrete, and so on).

 

In the absence of sufficient detail, the more sensible decision is to insulate the pipes. This is also recommended by BRANZ and the building code, even for hot water vent pipes.

 

 

It's not always beneficial - that was the exact point I was making. In the typical usage profile of a domestic installation and taking into consideration the volume of water in the pipes affected it's just not regardless of what BRANZ suggest. This is because despite the fact that though insulation slows heat loss through the pipe wall to the atmosphere the actual application of insulation to a pipe also increases surface area which on small diameter pipes can be a substantial increase thereby negating the value (W/m²) unlike the situation of insulating volume larger bodies where the surface area is largely unaffected by the addition of insulation. For this reason even reasonably large hot water pipes in manufacturing are rarely insulated in areas other than that for personnel protection.

 

If there's no financial benefit then what other benefit is there that is worth considering?

 

Financial return is a profit and is not the same meaning as financial benefit which also covers unprofitable benefits as with marginal pricing and tax losses.

I am also talking about practical levels of insulation rather than theoretical. For example, foam insulation is commonly available at half-inch (13mm) thickness or more. When I worked in and visited factories they commonly lagged their hot water and steam pipes.  It is also common to find statements like this.

Note that for most applications, the critical radius is so small. Thus, we can insulate hot water or steam pipes without worrying about the possibility of increasing the heat transfer by insulating the pipe.

Since the critical thickness is almost always a few millimeters, it is seldom (if ever) an issue for piping. Critical thickness is a concern however in insulating wires.

Yes, I also understand about the critical radius of insulation, where heat losses are at their highest - See http://www.geekzone.co.nz/forums.asp?forumid=141&topicid=185361&page_no=1#1431477  - and calculating the point where insulation saves money.

For those who don't understand, this blog has a graph illustrating the concepts http://eng-shady-mohsen.blogspot.co.nz/2012/07/critcal-economic-radius-thickness-of.html

In practice, it's too difficult for most people to calculate the points where thermal insulation is beneficial or profitable so I'd say that if you aren't sure then insulate. Most people would even have trouble calculating the relatively simple critical radius of insulation (m) = Convective heat transfer coefficient (W/mK) / Thermal conductivity of insulation W/(m2K): I calculate a critical radius of 3mm when choosing a low value for convective heat transfer to air (10 W/mK, to increase the point where insulation reduces heat losses) and using plastic foam (about 0.03 W/m2K).