sprinklers

Sprinkler first fix installation begun.

This week saw the start of the sprinkler system installation first fix under way. We need a sprinkler system (a form of fire suppression) as our plot fails to meet the technical standards in 3 key ways:

Fire vehicle access provision: every new house should have vehicular access from a public road (suitable for fire fighting vehicles) to not more than 45m from any door that gives direct access to the interior of the dwelling; our driveway is approximately 90m long;

Vehicle access routes: Fire and rescue service vehicles should not have to reverse more than 20m from the end of an access road. Where there is a dead-end route more than 20m long turning facilities should be provided; our plot is too narrow to provide adequate turning (we would have had to place our house more than halfway down the plot which wouldn't have worked for the passivhaus (and quality of living!) strategy of maximising the south facing elevation and garden area.

Public water supply: Generally every new house should be within 100m of a hydrant; due to the length of our drive we didn't meet this criteria in relation to the existing hydrants;

Whilst there are some qualifications to the above within the Standards, the net result in our instance was that the best way to tackle all three issues was to provide a sprinkler system throughout the dwelling.

The next step was the challenge of integrating this system into the design without adding a 'public building' feel to the house!

We have opted for 'concealed' heads which mean they just look like a small self-coloured disc on the wall or ceiling when the works are complete, rather than the standard head that projects from the wall that we are all used to seeing in shopping centres, galleries and other public buildings.

The installation will take place in several stages over the next few weeks in order to work around various other things happening on site simultaneously.

The first step was to test the mains water flow and pressure in order to ascertain what size of tank is required. As you can see above a hose is connected to the mains water... and then run outside to the back garden while the flow and pressure were monitored.

The sprinkler system is essentially fed from the tank however the mains pressure and flow can be accounted for, and can therefore supplement this supply, which in turn can potentially reduce the size of tank required. Unfortunately in our instance

neither the flow nor pressure are particularly powerful which means we needed a larger tank than first anticipated.

The tank is quite large (1200 x 600 x 1900mm) and due to the increase in size we had to temporarily remove some of the glulam posts in order to lower it into position from above - luckily the electricians were on site that day to lend a hand!

Say goodbye to that under-stairs cupboard and space for the upright vaccum cleaner! ... and hello to the irobot roomba that can live underneath a plinth! More on the dream of designing a 'home' for the roomba later....

Similarly to the ducting the sprinkler pipe work is being installed below the acoustic ceiling but within the lowered ceiling space of the inner box; this design keeps the installation compact, consequentially eliminating long lengths of pipe work which can create pressure losses, and importantly, reduces costs by reducing the number of heads required in total.

Our system designer and installer, William from Aquablaze (a local company with the relevant accreditation), undertook all of the design and calculations to make sure that the system has adequate coverage and supply to meet the relevant British Standard, as well as undertaking the installation on site.

The first photo below shows William working on the first fix pipe work... the second the installed pipes with the apparatus attached for pressure testing the joints.

The pipework is only 60mm outer diameter so is quite discreet and is fixed directly to the acoustic ceiling (taking care not to fix into the joists themselves!), which is another advantage of Fermacell as it can support a considerable weight on a single fixing, even on a ceiling. The pipes, fittings and junctions are connected and sealed using a proprietary solvent weld compound.

The heads themselves come in two parts: a first fix part with a protective cover, and the outer part of the head which can only be fitted once the final sheet material is fitted to the wall or ceiling. There is a frangilble bulb inside which breaks once a specific temperature is reached and which activates the system - contrary to all of the films you have seen only one head will activate at a time, which is part of the design consideration i.e. they can't be positioned too close to each other.

A typical concealed head

In our inner box area we are having an open lowered ceiling in the form of timber fins, which can present some issues with smoke detection and sprinkler head positions, as neither type of fitting can have any obstructions in front of it, and both need to be mounted on a solid plane for a minimum of 300mm all round to ensure the smoke or fire reaches the fitting first and does not bypass it.

We are going to solve this problem by varying the spacing of the fins, and making them come together around these fittings to create this required solid plane - more on this later!

All in all quite a lot of effort and expense for something you perpetually hope never needs used!