Considering that over 26% of heat is lost through our attic, insulting them is a must for heat loss prevention and modern sustainable living.

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Attic insulation comes in many forms from Spray Foam to Minerals Wool, Blown Fibre to Cellulose. Among this plectrum of materials, each with Pros and Cons, prices and differing installation methods it’s almost impossible to know which to choose from. Luckily, I’ve completed QQI Level 5 training at the SEAI Center of Excellence so I can help untangle this web of options and make sense of what to do and where.

There are 2 things that we need to understand to get attic insulation right:
1. Attic Insulation Type
2. Attic Draft Proofing


We could be here till tomorrow going through all the options and still be none the wiser so let’s take an easier approach. The centre of excellence for home energy upgrades in Ireland is the SEAI. They recommend that a B2 Energy rating should be achieved in all homes in Ireland. That's because a B2 rated home is considered the benchmark for excellent energy performance and home comfort.

It’s impossible not to lose heat through your building fabric e.g. Attic, Walls, Windows, etc. so we must think in terms of acceptable Heat Loss. The U-value is a measure of heat transfer (or heat loss) through the building fabric. The lower the number, the better the insulating performance. U-values generally range from 0.1 (very little heat loss) to 1.0 (high heat loss). And here is where the SEAI come in, they updated the Building Regulations in relation to home Energy in 2019 - Part L now includes the Energy Performance in Buildings Directive (EPBD) requirement for Nearly Zero Energy Buildings. The table below, taken from Part L, shows the u-value that we need to achieve for our attic i.e. Attic with a pitch roof and insulation at ceiling U= 0.16 W/m 2 K

With me so far? Just one more step to go. What type of material and how much of it (thickness) do we need? Thankfully, U-value takes care of this too. U-Value is made up of the materials thickness and its thermal conductivity λ. It’s a legal requirement that both are clearly marked on an insulating material. Don’t worry, we are not getting into formulas – here’s what I recommend - Knauf Earthwool Insulation 300mm.

This is what we used at the SEAI centre of excellence and here’s why:

  • Knauf Earthwool Insulation @300mm depth gives a U-Value of 0.15 W/m2K which exceeds the Building regulation standards.
  • Excellent thermal performance
  • Non-combustible A1 Euroclass Reaction to Fire classification
  • Lightweight quilt for ease of installation
  • It’s non-toxic unlike fibre-glass and Spray Foam Insulation
  • Attic Joists are generally 150mm so the first role is laid between the joists.
  • The second layer across the joist. This stops the thermal bridge caused by the joists.
  • It fits snug between the joists unlike rigid insulation which is always gappy.
  • A uniform depth of 300mm is easily achieved (ensuring we meet our 0.16 W/m2K target) unlike spray foam which is never a uniform thickness.

In the example above we have only covered attic insulation at floor level - Pitched Roof (Insulation at ceiling). You can also insulate at rafter level – Pitched Roof (Insulation on Slopes). However this is a bit more complicated as the U-Value must be determined by a combination of insulation between the rafters (probably Earth Wool) and insulation backed plaster slab (PIR usually). Therefore, we have 3 thermal conductivities λ to deal with Earthwool, polyisocyanurate and plaster board. Probably best to call me to chat through this one 087-6089310


We put attic insulation in place to stop our heat from escaping. However all the insulation in world will be ineffective if the heat leaves our living space due to badly sealed attic doors and down lights. This is an area regularly overlooked and thus heavily focus on during our training at the NZEB Centre
of Excellent.

Downlights - If the old halogen spot lights exist we need to replace them with LED’s as these run at a much lower temperature and are far more efficient. Plus they don’t take a half hour to heat up and give a much nicer

Pre-made covers now exist that cover the ceiling hole caused by downlights and rosettes. This cover must be sealed in place with specialist air-tight tape to create an effective seal.

The light cover is then covered with the Earthwool insulation. Packing it loosely around the fitting.

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Attic Doors - Some of the new attic stair systems come with pre-insulated and pre-sealed hatches. However if you have an older attic door or just a piece of plywood (which is generally the case) then not to worry – we have a solution for that too! Attic Door Insulation – This is one to really watch!

Hot air flows from warm areas in your home to cold areas so if the attic door is not insulated to the same U-Value as the attic then the entire door will
draw heat from your home. Practically, earthwool is not a suitable insulator as it would just fall off the door once opened so we need a rigid alternative
that can be glued to the door.

Polystyrene is the perfect answer as it’s rigid, yet amazingly light. You need to get the polystyrene thickness right to achieve the same U-Value as your attic insulation. Picture opposite which shows insulated attic door. Draft-Proof strips – These are then placed around the attic ope to prevent further heat loss. They must be placed in a location to be compressed when the attic door is closed.



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