Putting In Insulation: A Step-by-Step Installation Guide

Putting in insulation is one of the most cost-effective ways to make a home warmer, drier and cheaper to heat. Whether you are fitting it yourself or weighing up a professional install, this guide walks through what is actually involved - what to sort out before you start, how insulation goes in across the ceiling, underfloor and walls, and how to get it right so it actually performs.

Before you start

Getting the prep right makes the whole job faster and the result better.

• Work out how much you need. Measure the areas you are insulating and use our Area Calculator to estimate quantities. Our guide on how to measure your home walks you through it.
• Choose the right product and R-value. The right R-value depends on the area and your climate zone. See How to Choose a Product and What Are R-Values before you buy.
• Get your gear ready. Gloves, a dust mask, eye protection, long sleeves, knee pads and a sharp knife make the job safer and cleaner.

Putting in insulation by area

Different parts of the house lose heat at different rates, so this is where to focus your effort.

Ceiling insulation. Hot air rises, so the ceiling is the single biggest source of heat loss in most homes - around 46%, and up to 60% in some. Segments and blankets are laid snugly between the ceiling joists, then a second layer can be run across the joists to cover the timber and remove cold bridging. Keep clearance around downlights and heat sources. See our Ceiling Insulation Installation service for how we do it.

Underfloor insulation. Underfloor segments are friction-fitted or stapled up between the floor joists, fitting tightly with no sagging or gaps. It is awkward work in a confined space, which is why many homeowners have it done professionally. See our Underfloor Insulation Installation service.

Wall insulation. Walls account for around 25% of heat loss but are the hardest to retrofit, since the lining usually has to be off. Wall insulation is most easily installed during a build, a reclad or a renovation when the framing is exposed.

Getting it right

Correct installation matters more than most people realise, and it is where a DIY job most often falls short. A gap as small as a few millimetres can reduce the overall effectiveness of insulation by up to 50%. So the details count:

• Fit it snugly. Insulation should fill the space completely with no gaps at the edges or between pieces.
• Do not compress it. Squashing insulation to make it fit reduces its R-value - it needs its full thickness to work.
• Cut neatly around obstacles. Wiring, pipes and fixings should be worked around carefully, not crushed under the insulation.
• Mind the heat sources. Keep the required clearance around downlights, flues and transformers.

Once it is installed and the floor or lining is back on, you never see what you might be missing out on - so it pays to get it right the first time.

Staying safe while you install

Insulation work is not technically difficult, but it can be physically demanding and carries real safety risks.

• Take care in confined spaces like subfloors and roof cavities - know your exits and do not work alone.
• Keep clear of electrical wiring and maintain clearance around downlights and other heat sources.
• Wear the right protective gear and stay hydrated, especially in a hot roof space.
• If anything feels beyond you, stop and call a professional.

DIY or professional installation?

If you are keen to get stuck in, ceiling and underfloor insulation are achievable as a DIY job - it helps to rope in a friend or two. Walls, tricky access and large jobs are usually better left to a professional.

Elite Insulation installs across Auckland, with trained installers and a 5-year workmanship warranty, so the job is done right and you are covered.

Product installation guides

Manufacturer installation guides are provided as a reference for the products we supply. Use them alongside the steps above.

Pink Batts Glass Wool (Fibreglass)

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