Plumbing and Electrical Services

 Plumbing and Electrical Services

How do you deal with plumbing and electrical services in a Formance Structural Insulated Panel building project? It’s the first question for most people.

Quick answer:

Plumbing. Run pipes on interior walls if possible. If not, frame up a service duct on the interior face of the SIPs panels.
Electrical. Standard horizontal and vertical chases are provided in the panel core for cables to run in.

Formance panels are designed and manufactured to provide a high performance building envelope but must be correctly installed. Building science teaches us that stopping air is the second most important job of a building enclosure. The first being stopping the entry of rain! However, uncontrolled airflow through the building envelope also carries moisture into framing, causing rot and mould. This air movement can account for a large portion of a home’s energy consumption and can cause indoor air quality issues with subsequent health problems for occupants.

1.  Planning

The earlier in the design and construction process the builder and the sub trades are made part of the team with the homeowner and designer, the more efficient the building process will be.

First time SIP’s plumbers and electricians could be unsure of how to go about their work and could load their prices because of perceived risk. The builder must train and mentor these tradesmen and obtain their input into the design.

The builder should cover and agree the following planning issues with the plumber and electrician:

a) The change in sequence from conventional framing. Because the insulation forms part of the SIPs this will be complete before the plumber and electrician start on site, not after as with conventional framing.

b) Conduct a site meeting before these trades begin any work on site to ensure requirements and procedures are understood. Any issues to be resolved before work begins.

c) Review the panel layout drawings particularly pipe and cable runs, any building envelope penetrations and the tightness and weather proofing details. After final client sign off it may be necessary to again review these drawings to ensure any changes are understood and implemented.

2.  Plumbing

 Plumbing penetrations can be a major source of air leakage as holes in exterior walls cause drafts and air leakage.

Don’t put plumbing in or on exterior walls if at all possible, run pipes through timber or steel framed interior partitions. If this is not possible, frame up a service duct on the interior face of the exterior SIPs panels for the plumber to run his pipes in. If pipe runs have to be flush with interior wall surface of the SIPs panel, use a thinner panel in this area and build up the insulation thickness with foam or batts after the plumber has finished.

Plumbing penetrations through exterior joists should be sealed with expanding foam. Vent stacks should be combined with air admission valves where possible, and any vents penetrating attics or roof panels should be sealed with proprietary flexible seals to handle expansion of the pipes.

If it’s absolutely necessary for pipes to penetrate the exterior envelope (eg overflow pipes) do not drill a hole which is a tight fit with the pipe but a hole which is about 25mm larger in diameter than the pipe to allow a good foamed seal around the penetrating pipe. 

 Plumbers must advise and agree on:

a) The pipe runs and entry and exit points through the building envelope.

b) The fixing requirements for the plumbing fittings.

c) Any special attendance requirements from the builder or other trades.

 3.  Electrical

Any electrical or data cable penetrations of the exterior SIPs can also be a major source of air leakage and compromise the integrity of the building envelope. Cabling systems should be installed in interior walls wherever possible.

If this isn’t possible, there are two approaches to the installation of cables and boxes in exterior walls:

a) Cabling systems should be installed in interior walls wherever possible. 

If this isn’t possible, there are two approaches to the installation of cables and boxes in exterior walls:

- in service chases through panel cores or

- in perimeter baseboard chases. 

b) Perimeter baseboard chases are preferred. Formance SIPs have standard chases in the EPS (expanded polystyrene) core: one vertically in the centre of the panel and two horizontally, usually 250mm and 1000mm from the bottom of the panel. 

c) Service chases in panel cores should be sealed with expanding foam. Similarly, sealants can be used to seal penetrations in outlet boxes. If some, or all of the standard chases provided in the Formance SIP are not required they can be eliminated. Less is best for air movement.

d) Should non-standard chases in the panel core be required, it is possible to create these on site with a ‘hot-ball’ rod to melt the EPS core, an auger drill bit, a flexible drill bit and a hole saw. The panel should be oriented vertically when forming a chase. Use a black marker pen or chalked string line to identify core chases. 

e) Place light switches close to doors for ease of cable access. Bend cable end over and tape it. Push rather than pull cable through the chase – it’s easier that way.

f) Exterior power outlets require special attention to ensure they are properly sealed to prevent air movement.

g) Upper level access for cables can be achieved by drilling a hole in the capping plate of the lower level panel to align with the vertical chase in the core. A corresponding hole is then drilled through the bottom plate of the upper panel and into the EPS to the required height.

h) Sometimes an electrician must run cables in conduit which will require a 50mm diameter chase to be created. Be careful that the conduit is not pierced by subsequent roofing or lining fixings.

Perimeter baseboard chases are preferred. Formance SIPs have standard holes in the EPS (expanded polystyrene) core: one vertically in the centre of the panel and two horizontally, usually 250mm and 1000mm from the bottom of the panel. Service chases in panel cores should be sealed with expanding foam. Similarly, sealants can be used to seal penetrations in outlet boxes. If some, or all of the standard chases provided in the Formance SIP are not required they can be eliminated. Less is best for air movement.

Should non-standard chases in the panel core be required, it is possible to create these on site with a ‘hot-ball’ rod to melt the EPS core, an auger drill bit, a flexible drill bit and a hole saw. The panel should be oriented vertically when forming a chase. Use a black marker pen to identify core chases.

Place light switches close to doors for ease of cable access.

Bend cable end over and tape it. Push rather than pull cable through the chase – it’s easier that way.

Exterior power outlets require special attention to ensure they are properly sealed to prevent air movement.

Upper level access for cables can be achieved by drilling a hole in the capping plate of the lower level panel to align with the vertical chase in the core. A corresponding hole is then drilled through the bottom plate of the upper panel and into the EPS to the required height.

Sometimes an electrician must run cables in conduit which will require a 50mm diameter chase to be created. Be careful that the conduit is not pierced by subsequent roofing or lining fixings. 

Electricians must advise and agree on:

a)  Cable runs in the walls, ceiling and roof.

b)  Switch and plug positions.

c)  Location of all light fittings and fixing requirements – particularly light fittings.

d)  Entry point, meter and main switch board positions and method of sealing against water entry and air movement.

e)  Position of any exterior outlets and sealing method.

f)  Any areas where cables are required to run in conduit.

g) Any special attendance requirements from the builder (eg. cutting box openings in the SIPs) or other trades

All the above information should be shown on drawings – preferably the panel layout drawings.

Plumbers and electricians generally agree that with good planning, documentation and site coordination, a SIPs job is comparable in price to conventional framing- if not cheaper- because there is no requirement to cut notches and drill holes in studs and nogs (dwangs) for their services.

While this might sound complicated and difficult, these factors have been considered and resolved many times already by the Formance Panel team.

Contact them on (0800) 000 527 to talk to Nino, the Formance Design Support Manager.

 

Honour Your Craft, Study Your Trade


Builders’ Blog  – by Peter White

Straight, Level and Plumb is a blog for builders by Peter White. With 45 years of construction experience under his belt and deep interest in SIPs Peter is well placed to advise on the adoption of this technology in New Zealand. Find out more about Peter and his interest in SIPs. 


 

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