5 tips to keep your building cool yet energy efficient this summer

21 Jan 2014 by Annette

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With temperature records tumbling already this summer – and energy bills soaring – here are five tips to keep your building cool yet energy efficient.

1. Update HVAC set points

A set-point is the temperature and humidity level which your Heating, Ventilation and Air Conditioning (HVAC) aims to keep the internal environment of your building.

We all know that increasing temperature set points in summer will reduce energy use because your air-conditioning doesn’t have to work as hard to cool you down. The rule of thumb is that every 1°C change can cut cooling costs by 5-10%. A typical set-point in summer might be 22°C, but you should find that a higher set-point of around 24 or even 25°C will still provide an adequate level of comfort.

Cold in officeIncreasing the set point can also actually improve comfort levels for staff by reducing the big difference between inside and outside temperatures in summer. How many of your staff keep a cardigan at work in summer because your air-conditioning is too cool for summer weight clothing?

You should chat to your mechanical contractor about this and depending on your control systems you might find you have even more flexibility with how you can manage set-points for your building to balance energy use and thermal comfort. For example you might have the ability to set a low and high set-point (i.e. an acceptable temperature range), or even a floating set-point that adjusts automatically to follow outside temperature.

2. Review HVAC run-times

In Australia we tend to have more public holidays in summer so make sure your controls systems are up to date and you aren’t running your air-conditioning when people aren’t going to be in the building.

But sometimes there is a case for running your HVAC more outside of normal operating hours. In summer it may be worth adjusting run-times to keep your building cool. If you are expecting a run of hot days, then running your HVAC plant earlier or longer may actually reduce energy use and just as importantly reduce your maximum demand by stopping heat building up (and avoiding the need for your plant to work too work extra hard to cool the building back down again).

Depending on where your building is located and your tariffs you might find that reducing your maximum demand has a bigger impact on your energy costs then reducing energy use.

While you are working with your mechanical contractor on set-points and run-times you also make sure temperature sensors are properly located; fans, filters and ducts are properly cleaned; and, that you are making proper use of outside ventilation (while in general outside ventilation is a good thing, you don’t want to be transferring too much heat and humidity into the building).

3. Reduce heat from lighting

The cost of LED lighting continues to fall and while LED lighting can reducing energy use, did you know they are one of the coolest lamp types and so can reduce air-conditioning costs.

To keep your building comfortable your HVAC system has to mitigate all the heat generated by the people and equipment in your building, and the lighting. By switching to cooler running lights and switching off lights that aren’t required you reduce the heat load.

If you’ve been having trouble making the business case of a lighting upgrade stack up, try calculating the air cooling energy savings too and this may help get the project over the line.

4. Consider solar power

Just like LED lighting, the cost of roof-top solar arrays continues to fall and we’re now regularly seeing pay backs of less than 5 years for commercial systems. While retrofitting a roof-top PV system onto a commercial office tower can be challenging, many commercial buildings are very well suited to retrofitting roof-top PV including shopping centres and ‘big box’ warehouse-style retail buildings, light industrial facilities, and recreation and aquatic centres.

Screen Shot 2014-01-21 at 9.21.56 AMAnd also just like LED lighting, there may be a cooling benefit from PV that you haven’t considered. Solar panels can be very effective rooftop insulators. The panels act as shades, preventing the the sun radiating down directly onto the roof. While panels do heat up, much of the heat is removed by air movement between the panels and the roof.

Lastly when considering a renewable energy project for your building, you should consider the possible demand reduction benefits of the system, especially if you are considering a larger system (e.g. > 150kW). High solar irradiance in Australia often coincides with building and network max demand so depending on your tariff your solar system could also save you money by reducing demand and capacity charges.

5. Review shading and blinds

One major source of heat in commercial buildings is through glazed doors and windows. This can be the source of up to 50% of unwanted heat gain during summer. Modern buildings designed following Ecologically Sustainable Design (ESD) principles will incorporate modern window systems with double glazing and low emissivity glass, active or passive shading systems, and window coverings like blinds to reduce heat gain.

If you have these kinds of systems in your building, make sure they are properly maintained and working. Also make sure staff know how and when to use blinds to keep heat out, and when to let light in. If you don’t have good shading systems for your building then this is something you should consider investigating with the help of an ESD consultant.

And if you have the ability, consider planting shade trees as one of the best upgrades you can make to your building. Some studies have found that tree planting can account for a 25% reduction in cooling energy requirements. And trees can have an enormous benefit in improving the amenity and appearance of your building, so why not plant a tree today!

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