Sustainable water heating for townhouses and apartments

All architectural practices are busy designing the best buildings to fit land and budget available. We’ve all got an eye on sustainability because we know it’s an important issue while competing demands on our time mean it’s hard to be across the fine detail of all issues. Hot water is a back-of-wall service, not as captivating to our clients as eye-catching façades and stunning interiors. But not providing your clients with a hot shower in their new townhouse or apartment is unthinkable.

So, we tend to fall back on hot water systems we’re familiar with. Could there be better ways to deliver this critical and high-impact service? Let’s break down this complex issue:

Heating water is the largest single energy demand in modern residential buildings. It therefore provides the greatest opportunity to reduce living costs and the environmental impact of the building once in use.

Residential buildings have predictable hot water use so designing out fossil fuel use in this long-lasting infrastructure is easy and a high priority. These systems can be designed in from the outset; especially important in townhouses and apartments where retrofitting renewable technology is much more complex or potentially impossible.

Resilience of energy supply is really important when you want to guarantee a hot shower every day. Natural gas or LPG are often used for water heating in dwellings with smaller footprints or shared services but there is very serious vulnerability in NZ gas supply, with rationing and cost rises occurring now and set to increase with population growth.

When we burn gas we are releasing fossilised carbon, contributing to the climate crisis. Keeping it electric or solar reduces the climate impact, cycling carbon from the current account rather than borrowing from future generations’ climate stability.

There are a range of sustainable technologies that meet every budget and design of townhouse or apartment. The keys to success are reliable performance modelling, complete system design and guaranteed product operation. Get in touch with us to guide you through this:

Water efficient design 

Specify low flow shower heads, preferably >7.5L/min and aerating taps to reduce hot water use, making any heating system more efficient.

Electric elements & night heating only

Use a standard cylinder in each dwelling, with overnight heating only by electric element to utilise renewable, hydro electricity from grid.

Pros – minimised carbon emissions from off-peak electricity, lowest cost system, metering included in electricity bill.

Cons – cylinders must be big enough to store hot water for morning & evening use. Only reduces environmental impact with night time heating controls. No Homestar points.

Solar hot water 

Individual systems for townhouses; centralised system with hot water ring main for apartments. Electricity, wood pellet or gas fired additional water heating.

Pros – provides on-demand hot water 24 hours per day. A high quality, appropriately specified solar system will reduce energy use and costs by up to 95% in summer, averaging 75% in townhouses and 60-70% in apartments over the year. 6 Homestar points available.

Cons – upfront cost greater than non-renewable system. Apartments’ distributed hot water requires metering and billing or inclusion in fixed charges. Complete system design and guaranteed product performance to ensure savings. Townhouses require adequate cylinder size to store hot water.

Hot water heat pumps 

Individual units for townhouses; distributed split units with separate cylinder or centralised large plant for apartments. Some systems require additional electricity for boosting temperature and/or ring main heat loss.

Pros – provides on-demand hot water 24 hours per day. High quality, appropriately specified heat pump system will reduce energy use and costs by an average of 60% - 75%. Highest performance individual systems do not require boosting electric element.

Split systems provide solution for apartments and townhouses with indoor cylinder & outdoor compressor. No roof mounted panels.

Cons – upfront costs greater than non-renewable system. Individual systems require a cylinder in every dwelling. Cylinders need to be adequately sized to meet demand. Individual compressors must be quiet enough for higher density dwellings. Centralised systems generally require additional heat boosting.

Pellet boilers & ground source heat pumps (GSHP)

Only suitable for centralised hot water systems for larger or multiple buildings. DHW system is usually combined with space heating.

Pros – highly sustainable, renewable fuel (pellets), or high performance use of electricity (GSHP). Centralised hot water doesn’t require cylinders in each dwelling.

Cons – higher capital cost than non-renewable system. Storage area needed for pellet fuel. GSHP pipes need to be in ground.higher-density