plumbing #2
Plumbing first fix progresses...
Over the Christmas holidays we progressed the plumbing first fix. In principle this is no different to a standard house, with one exception: the quality of installation for the pipe insulation required. In fact the quality of the insulation install should really just be considered best practice, however this is rarely executed on site in more 'standard' projects. Generally speaking it is not uncommon to see pipe insulation missing from pipe clip positions, joints (elbows, T's, etc.), valves and other fittings. All of these omissions can lead to measurable and perceptible losses within the system, which in turn increases the energy consumption of the system as it or the user attempts to compensate, and an increased ambient temperature in the spaces where these pipes run and the services all come together (for example in the cylinder cupboard, utility or plant room), which can lead to overheating.
The photos above show the pipe insulation installation process in the kitchen before the units were fitted (the valves will be insulated later once the pipework is finished to the tap).
There are 4 main reasons to insulate pipework (and the same principles apply to ductwork): to control condensation; to control surface temperature; to protect against freezing if the pipework is out with the insulation envelope; and to control heat transfer.
As we have low flow fittings everywhere we decided to use 15mm pipework throughout to minimise the increased standing losses from larger diameter pipes: standing losses occur between draw-off times as the water in the hot feed pipe cools and transfers that heat to the surrounding air. Insulating the hot water pipework reduces the effect of this by slowing the heat transfer process, and helps to keep the hot water hot right up to the point of delivery. Similarly, the cold water pipework should be insulated, particularly if it is copper, to prevent condensation forming on it and the consequential damage to surrounding fabric that can occur as a result. During winter we witnessed our plastic cold water mains pipe covered in condensation (before it was insulated!) as the ambient temperature was around 18 - 20 degrees and the cold water from the mains was much colder (probably only about 4 - 5 degrees generally), so this is a very real phenomenon! Condensation can often be mistaken for a leak which is another important reason to prevent it occurring.
In the Technical Standards 'Building Services Guide' there is a table which helps to guide the installer on the maximum heat loss from a pipe of a given diameter (under certain assumed conditions), and the Energy Saving Trust website recommends a minimum thickness of 25mm. Depending on the insulation conductivity and pipe diameter a thickness for a given heat loss can be calculated. BS 5422: 2009 lists tables that calculate this for a variety of pipe diameters, thermal conductivities and emissivities of insulation, and types of pipe / duct material (such as steel, copper and plastic).
We used 25mm thick Climaflex polyethylene insulation, as it is a reasonable balance between performance and cost. The conductivity ranges from 0.034 - 0.038W/mK, depending on temperature. (At the time we purchased this we didn't realise that it is also available with a self-adhesive closing strip so we used tape to ensure it was sealed.)
Following the passivhaus strategy of compact services arrangements we have our HWC approximately in the centre of our plan, and all of the wet rooms are as close as possible to this in order to minimise the plumbing runs required to each tap, WC and shower.
We also have a Recoup Energy Solutions vertical WWHR unit which takes the heat from the waste water from the master bedroom shower and transfers this to the cold water supply to the same shower effectively pre-warming the cold, which reduces the amount of hot water needed, with any surplus going to a separate cold water inlet on the HWC. (This is a twin walled unit to prevent any risk of cross-contamination: it is the grey cylinder in the photo below, and you can see the feed pipe connection points on the left, and the main waste pipe connection points at the top and the bottom.)
Larger diameter pipes and fittings, such as the mains water supply, are insulated using a roll of 25mm Armaflex insulation. The shut-off valve also gets an insulated cover... I made a small plug from the same insulation that can be easily removed to access the shut-off valve.
The plumbing behind the bath / shower in the main accessible bathroom is a little crowded as we have the bath valves mounted on the side wall so these need to branch both up to the shower and down to the bath filler. This next photo is half way through the insulation process.
For a sharp bend I made a 'hockey stick' from insulation by creating cut outs on the inner side of the curve... Then bending the insulation… Then taping it into position...
And finally fitting it over the curved hose.
The final insulated pipework behind the bath & shower.
Shown below is an example of a shut-off valve that was insulated using a small section of the same thickness of insulation as the main pipe: small additional pieces were added to complete the 'wrap' around the pipe and the whole assembly taped in position.
