When building a new home, energy efficient homes have become top of the wish list lately for many homeowners. Everything from smart appliances through to heating, ventilation, and air conditioning are all good at doing their part to save on energy costs – but did you know that a home’s energy-efficiency extends all the way to the roof? In fact, your roof can be one of your biggest weapons against high energy costs. So how do you choose an energy efficient roof? Here’s what you need to know.
What Makes A Roof Energy Efficient?
Roofing energy efficiency comes down to everything from the materials used, the actual roof design, and how it’s installed through to the colours and coatings of the roof cladding – even insulation and ventilation systems are important! All of these plus more influence your roof’s energy efficiency, so let’s take a closer look.
1. Solar Reflectance Index (SRI)
The Solar Reflectance Index is a common metric used to express the percentage of sunlight reflected away by your roof, which basically equates to how hot your roof gets in the sun. Generally speaking, the higher the SRI, the more energy-efficient the roof is.
There are two main factors to the SRI; the design of your roof, and the materials used (and their colours). Reflective colours can help in reducing heat absorption by reflecting the majority of the heat, ultimately keeping the building cooler, aiding longevity and lessening the strain on internal air conditioning systems.
2. Ventilation And Roofing Insulation
Airflow is critical to a roof’s energy efficiency because it allows hot air to escape and cooler air to circulate. Lessening heat build-up under the roof reduces the need for air conditioning in the summer and keeps the roof temperature more consistent during winter. Without proper ventilation, the build-up of heat in your roof space will transfer to the inside of your home. These temperatures can not only raise your power bill, but they can actually damage your roof due to moisture build up and exposure to extreme heat/cold. Static, electric and wind-powered vents are the three main types of roofing vents used in roofing systems in NZ.
In conjunction, a well-insulated roof helps by preventing heat loss in colder months and also heat gain during warmer months. Insulation levels, therefore, significantly affect maintaining more constant temperatures inside the building, greatly reducing the need for additional heating or cooling.
3. Thermal Mass/Resistance
Rooftop temperatures have been known to get 30 to 40 degrees hotter than the outside air temperature. The thermal mass concept relates to the roof’s ability to store this additional heat and resist/encourage heat transfer. The concept of thermal mass works within the roofing system and materials by either reflecting away excess heat, or absorbing heat, which in turn affects the internal temperatures of the home.
Roofs with higher thermal mass are better at maintaining temperatures and therefore better at sustaining more constant temperatures within the home, resulting in less energy use overall.
Do Energy-Efficient Roofs Really Save You Money?
What are the long-term cost savings and environmental benefits of energy efficient roofing? Broadly speaking, energy-efficient roofs pay for themselves over their lifespan. They can lower your power bills, reduce strain on HVAC and air-conditioning systems extending their lifespan, and even extend the lifespan of your roof by preventing deterioration caused by extreme temperatures.
What Type of Roof Is the Most Energy Efficient?
Choosing your roofing type carefully is one of the best strategies for maximising energy efficiency in the home. Here is a quick review of the most energy efficient roofing types.
- Metal Roofing. Long run roofing iron is by far one of the best choices you can make for your roof in general. Lasting over 50 years in most cases, metal roofing is the most energy-efficient roof in NZ for residential installations, plus it requires very little maintenance. Why are metal roofs energy efficient? They are naturally very reflective and hardwearing (which is why they are hot to the touch).
- Tile Roofs. Also a good energy-efficient roof choice but requires some extra effort. Tiles are usually made from clay or concrete here in NZ, so do require pre-treatment to maximise heat reflectivity but they do have good thermal properties with the ability to store heat during the day, releasing it as temperatures cool. Tile roofs are a good choice where maximising airflow is a priority or in dry climates.
- Green Roofs. Green roofs or living roofs, are generally flat roof designs covered with vegetation. This vegetation provides natural insulation and cooling throughout the day significantly reducing heat absorption while also improving air quality. The initial and ongoing investment for a green roof is likely to be more expensive than other roofing options and these types of roofs are generally limited to apartment buildings or city dwellings.
Roof Design And Its Impact On Energy Efficiency?
Maintaining roof temperature using design elements primarily comes down to two factors – the colour and the pitch.
Most Energy Efficient Roof Colours – Lighter vs Darker
Darker, non-reflective colours and materials (such as black asphalt) tend to absorb rather than reflect heat. On the other hand, lighter colours and more reflective materials (such as white metal roofing) are better at reflecting heat.
White metal roofing is widely considered the most energy efficient roofing in hotter areas due to its high reflectivity (it reflects between 60% and 90%) however, other colours, such as light grey or light brown work well too. Darker-coloured roofs also have energy-efficiency properties if you live in areas where colder temperatures are the norm. It is best to speak with your roofing contractor to discuss the best roofing options for your location.
Most Energy-Efficient Roof Shape
Flat and pitched roofs are installed and constructed in different ways, so your roof shape will have an affect on what roofing materials you can utilise in order to achieve the best energy-efficient roofing.
Flat roofs, which are common in commercial situations, are typically constructed using a membrane system that can be naturally reflective depending on the coatings (and energy-efficient). Pitched roofs, which are common among family homes and residential areas in NZ, generally have metal roofing or tiles installed.
What Are The Benefits Of An Energy Efficient Roof?
Energy efficient roofing can do more than just save you money on your energy bills, these are just a few of the main reasons for installing an energy-efficient roof on your home.
- Adds to your property and therefore resale value
- Helps your HVAC and air conditioning systems work more efficiently
- Improves living conditions inside the home
- Lowers electricity demand by reducing air conditioning needs and therefore energy costs
- Good for the environment (reduces the amount of energy needed to cool buildings)
- Potential to extend the life of your roof by decreasing everyday roof temperatures and therefore heat-related deterioration
Tips For Improving Your Roof’s Energy Efficiency
Unfortunately, we are not all able to replace our roof immediately to increase energy efficiency, but there are a few small things you can do to make sure your roof is in tip-top shape and performing the best it can.
- Identify Potential Issues ASAP. Regular inspections are the best way to keep an eye on your roofs condition and pick up any problem areas before they develop into something more serious.
- Carry Out Regular Maintenance. Annual maintenance routines are great for keeping on top of roofing issues without ending up with massive bills. Whether there has been a particularly blustery storm or an exceptionally hot summer, regular maintenance can help identify any potential problems before they become major issues, saving time and money in the long run.
- Insulation/Ventilation Upgrades. As discussed earlier, poor insulation or ventilation works against your roofing system and makes it harder for your aircon and HVAC systems to do their job regulating your building’s internal temperatures. So taking the time to upgrade ventilation or insulation can be an easy, quick fix for many roofing systems.
- Think About Solar Power. Another great energy efficient roofing idea is to consider installing a solar power system. Solar panels both deflect some of the heat from the building and generate your own electricity.
If you’re unsure what the best course of action is for your circumstances, the team at Action Reroofing are happy to discuss your energy efficient roofing options.
