Wall insulation acts as a barrier to heat flow and is needed to keep your home cool in summer and warm in winter. Properly installed insulation helps to reduce greenhouse gas emissions and heating bills, as well as improve the overall comfort of your home.
Which R-Value Should I Choose For Wall Insulation Batts?
At Pricewise Insulation, we recommend that you consider upgrading your wall insulation to at least one ‘R-value’ higher than the mandatory specifications on your report. Furthermore, we also recommend installing internal wall insulation, both from an acoustic perspective and a thermal perspective. The acoustic considerations relate mainly to the isolation of sound between rooms. The thermal considerations are usually less important internally, since the main purpose of thermal wall insulation is to restrict temperature transfer between the outside and inside of the house. However within the house itself, you might find that there is a case to insulate the internal walls, for example if some areas of the home are likely to be used a lot more than others – you may wish to heat or cool only the kitchen and living areas during the day, and heat and cool only the bedrooms and bathrooms during the evening and night time. A properly designed air-conditioning system, partnered with internal wall insulation, will enable you to achieve this with as little wasted energy as possible.
Reasons to Install Wall Insulation Batts
Between 15-25% of heat losses and gains can occur through the walls of an uninsulated home. The only time to insulate your walls is during building or renovation, so it is important to install the right products in the walls of your home. The main thing to keep in mind when considering your internal and external wall insulation options, is that once the walls are lined, the job it done, and you won’t be in a hurry to dismantle the wall to redo the wall insulation. So, it’s imperative to ensure that 1. The correct R-value is installed the first time 2. The insulation is installed with a neat finish, with minimum air-gaps. New houses will usually be specified as having a mandatory R-Value installed in the ceilings and the walls. The basis for this is the requirement for all new homes to meet the minimum energy efficiency standards – and insulation in walls place an important role in achieving this standard.
You are faced with several insulation brands and do not know what to choose. In the end the biggest factor to consider is what R-value to use. Knauf Earthwool, Pink Batts and Bradford Gold Batts are all good quality brands, each with their own benefits.
The important thing to know is that products with the same R-value all have the same insulating performance if installed as specified. The density (or acoustic performance) might be different, but the thermal performance is the same. An R2.0 Knauf Earthwool Insulation Batt will provide the same thermal resistance as an R2.0 Fletcher Pink Batt or an R2.0 Bradford Gold Batt.
Why are R2.5 Ceiling Batts Cheaper Than R2.5 Wall Insulation Batts?
You might have noticed a difference in pricing between the R2.5 wall batts and R2.5 ceiling batts. Achieving an R2.5 rating within a 90mm product requires an increase in product density, hence the higher manufacturing costs. A typical R2.5 ceiling insulation batt is 125mm thick and not suitable for a wall cavity. Trying to compress the insulation into a 90mm cavity will cause the plaster to bow and will also reduce the thermal performance of the batt. If bulk insulation is compressed, so are the air pockets within it that provide the insulation. This means it will not work as effectively as it should, hence this approach is never recommended.
Pricewise Insulation are the wall insulation specialists. We deliver to building sites and homes right across Australia. Metro orders are shipped within 1-2 business days. For urgent deliveries please give our team a call on 1300 729 639.
Upgrading Wall Insulation Batts From R2.0 to R2.5
Upgrading to an R2.5 wall insulation batt will improve both the thermal and acoustic performance of your home. These batts are rigid and fit snugly between the wooden joists to achieve an optimal thermal finish. R2.5HD Knauf Earthwool and R2.5HD Fletcher Pink Soundbreak are high density products with higher acoustic ratings than your typical R1.5 or R2.0 wall batts.
Passive Design Techniques
Shade from trees, sails, eaves and window awnings are just a few passive design techniques used to increase building performance. Building orientation is another important consideration. A house that is fully exposed to the sun will experience a build-up of heat that the insulation will keep in and create an ‘oven’ effect. You can read more about passive design here.
Calculating Internal Wall Insulation Batts Cost Per m2
It’s quite simple to calculate how many bags of insulation you will need for your project. The basic steps are as follows.
• Measure the total area to be insulated
• Deduct any other areas not requiring insulation such as windows and doors
• Multiply the number by 0.9, to allow for the fact that the framing also takes up around 10% of the total area to be insulated
• Divide this number by the number of m2 in a bag of insulation
Here’s an example to demonstrate:
You have a house which is to be insulated with R2.0 Earthwool Wall Batts. The wall joists are at 450mm centres, so you will need the 430mm wide batts.
• Wall area is 185m2
• Deduct 45m2 of windows and doors = 140m2
• 140 x 0.9 = 126m2
• One bag of Earthwool R2.0/430mm contains 15.9m2 of external wall insulation
• 126m2 divided by 15.9m per bag = 7.9 packs
• Simply round up to the nearest pack = 8 packs
Minimum Wall Insulation Batt Requirements
The required total R-value for the building fabric of your home will vary depending on where you live in Australia. The Building Code of Australia (BCA) determines the minimum wall insulation requirements for your climate zone. Another influencing factor is how high your building site is above the Australian Height Datum (the mean sea level used for altitude measurement in Australia). We also sell wall insulation to customers living in New Zealand.