Insulation is one of the best investments you can do in your home. We are saying investment because it’s more than just a construction project. If you have to choose which part of your home to insulate, then start with the attic.
Why the attic and what is the best insulation – read in our comprehensive blog.
Why Insulating Your Attic Is Worth It
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The attic is one of the spaces in the home where the most heat loss happens. Not only that, it’s the first place in the summer from where hot air gets inside of the home.
There are several crucial benefits of insulating your attic for the hot and cold days, especially if you’re planning a full attic conversion later on.
Lower Bills
As we said in the beginning of the article, insulation is an investment. By insulating your attic you will significantly lower your energy bills all year round and make your home more energy efficient.
Attic insulation helps prevent heat from escaping in winter, lowering heating bills, and keeps hot air out in summer. This means your electrical system won’t have to work as hard, reducing your heating and cooling costs significantly.
Protection of Your Home
Good attic insulation is a way to protect your home from the elements.
Insulation can help prevent condensation and moisture buildup in your attic, which protects against mould, mildew, and eventual wood rot. This preserves your home’s structural integrity over time.
Improved Indoor Air Quality
A good insulation of the attic will reduce the chances of outdoor pollutants, allergens, and dust entering your living space. This can make a noticeable difference, especially for allergy sufferers.
Even if you don’t have energy, the better air quality is beneficial for your health.
Improved Home Comfort
By insulating your attic space, you will indirectly improve your home comfort. If certain rooms in your house are drafty, too cold in the winter, or stuffy in the summer, poor attic insulation could be the culprit.
Proper insulation evens out indoor temperatures, making your home more comfortable throughout the year.
Increased Resale Value
In some cases, insulating your attic can be a costly procedure, the most substantial benefit of all is that by doing so you will increase the value of your property.
Energy efficiency is a major selling point. A properly insulated attic can improve your home’s energy performance rating and appeal to eco-conscious buyers, potentially increasing resale value.
Assessing an Insulation’s Effectiveness (R-value)
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When you need to assess your attic’s insulation, there’s one key figure you will come across everywhere and that’s the R-value.
R-value is the key metric to understand. It measures how well a material resists heat flow — the higher the R-value, the better the insulation. It is expressed in m²·K/W in Ireland and most of Europe, equivalent to RSI-value.
The recommended R-Value for different types of attics and roofs is given by the Irish Building Regulations (Part L – Conservation of Fuel and Energy).
You will find the key guidelines in the table below.
| Area | Recommended R-Value | Typical Thickness (Mineral Wool) |
| Attic / Roof (Cold) | R 6.5 – 7.0 m²·K/W | 300 mm |
| Pitched Roof (Warm) | R 5.0 – 6.0 m²·K/W | 150–200 mm (between rafters) |
| External Walls | R 3.7 – 4.0 m²·K/W | 100–150 mm |
| Floors | R 2.5 – 3.0 m²·K/W | 100–150 mm |
Other key factors you have to consider if you’re a homeowner in Ireland are the climate and the material you are going to use for insulation.
Ireland has a mild but damp climate and it requires insulation that can also handle moisture. Breathable material like sheep’s wool or mineral wool are ideal for that type of climate, because that way you will eliminate any moisture inside.
If you plan on checking the insulation in your attic by yourself, you have to take a measurement of how much insulation you have. If you have around 100 mm, then your R-value is probably around 2.8. To meet current standards, topping the insulation up to 300 mm is usually needed.
If you want a professional to assess your attic insulation, then you can hire a firm specialised in energy audits or a BER assessor.
What Is the Best Insulation for an Attic
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Once you’ve assessed what is the current state of your attic insulation, you have to decide on the material you are going to use for your project.
Here we will take a look at some of the most commonly used materials and their pros and cons.
Fibreglass Batt or Roll
Fibreglass batt or roll insulation is one of the most common and affordable types of insulation used in residential homes — especially for attics, walls, and floors. It’s made of tiny glass fibres spun from molten glass and bound together to form soft, wool-like mats.
The batts come in pre-cut panels, designed to fit standard joists spacing. The rolls are a long and continuous sheet you can cut to size.
The pros of this material include:
- Cost-effectiveness – this is one of the cheapest insulation options available on the market.
- DIY-friendly – it is easy to install in open attics with accessible joists. It is also lightweight and easy to cut.
- It’s non-flammable – fiberglass won’t burn, making it a safer option from a fire-resistance standpoint.
The R-value of this material is around R 2.5 to 3.0 per 100 mm thickness. For reaching the recommended R-value you can layer the material.
The cons of this material are:
- Not effective when compressed – the material has to be fluffed up and properly fitted.
- Sensitive to moisture – this material doesn’t stop moisture on its own and can get mouldy.
- Health concerns – fiberglass can irritate the skin, eyes and lungs.
- Potential air leakage – fiberglass doesn’t stop air movements, so drafts can still pass through.
If your attic is prone to moisture, maybe fiberglass is not the best option in material for insulation.
Blown-in
Blown-in attic insulation, also called loose-fill insulation, is a type of thermal insulation that’s applied by blowing or spraying loose fibres into attic spaces using a special machine. It’s ideal for covering irregular, hard-to-reach, or already insulated areas that need topping up.
It’s commonly made from cellulose, fibreglass, or mineral wool.
The pros of this material include:
- Excellent coverage – fill all gaps, nooks and shapes in your attic.
- Fast installation – a whole attic can be done in a few hours’ time.
- Good air sealing – if cellulose is used, it provides some air-blocking benefits, reducing drafts.
- Eco-friendly – it’s made from up to 85% recycled materials.
This material also has a very good thermal performance and it’s easy to layer.
The cons of this material are:
- Needs equipment – requires a special machine and ideally two people to install.
- Settling over time – blown-in cellulose can settle by up to 20%, reducing R-value unless compensated with extra thickness during installation.
- Moisture sensitive – if exposed to leaks, it clumps or grows mould, especially cellulose.
- Messy to install;
- Difficult to remove.
You have to avoid blown-in insulation if your attic has poor ventilation or active leaks.
Spray Foam
Spray foam attic insulation is a high-performance insulation type that’s sprayed in liquid form and then expands into a solid foam, sealing cracks, gaps, and voids in the attic. It’s one of the most effective but also most controversial insulation options — especially in Ireland.
The pros of this material include:
- Exceptional air sealing – creates an airtight barrier, preventing drafts and air leakage.
- Eliminates moisture – adds resistance against moisture intrusion.
- Long lifespan – durable and stable once cured, doesn’t sag, settle, or degrade easily.
- Improves structural strength – closed-cell foam adds rigidity to roof structures, acting as reinforcement.
This material has a very good R-value if installed properly.
The cons of spray foam insulation are:
- Very expensive – it can cost 2 or 3 times more than fibreglass or cellulose.
- Requires professional installation – must be installed by certified contractors using specialised equipment. Improper application can lead to off-gassing or health issues.
- Ventilation complications – completely seals attic spaces, which can trap moisture if ventilation isn’t redesigned properly.
- May nullify roof warranties – sealing roof timbers can block visual inspections, potentially voiding warranties or affecting home resale value.
- Difficult to remove – once applied, removal is labour-intensive and expensive. This can be problematic if roof repairs or future insulation changes are needed.
In Ireland, many mortgage lenders, BER assessors, and surveyors flag spray foam insulation as a red flag due to trapped moisture under roofing felt.
Sheep’s Wool
Sheep’s wool insulation is a natural, breathable, and sustainable alternative to conventional insulation materials like fibreglass or foam. It’s increasingly popular in eco-conscious home builds and retrofits — especially in damp climates like Ireland, where its moisture-regulating properties shine.
The pros of sheep’s wool insulation include:
- Natural and sustainable – 100% renewable, biodegradable, and recyclable.
- Moisture-regulating – wool absorbs and releases moisture without losing thermal performance — ideal for Ireland’s humid conditions.
- Non-toxic and safe to handle – no protective gear needed, ideal for DIY projects.
- Long lifespan – properly treated wool is resistant to fire, mould, and pests, thanks to boron or natural salts.
This material is excellent for the humid climate of Ireland.
The cons of sheep’s wool are:
- More expensive upfront – may not suit tight budgets for large-scale retrofits.
- Less availability – may require ordering from specialist suppliers.
- May require thicker layers – slightly lower R-value per cm means you might need more thickness to meet the Irish attic standard.
- Needs proper treatment – must be treated to resist insects and fire, untreated wool can be vulnerable to pests or degradation.
As you can see, there’s a lot to consider for such an expensive option.
Multifoil
Multifoil insulation is a thin, reflective insulation material made of multiple layers of foil, foam, and wadding. It’s known for its compactness and ability to reflect radiant heat, making it useful in specific situations.
The pros of this material include:
- Space-saving – ideal for areas with limited depth, like loft conversions, dormers, or behind stud walls.
- Easy to install – lightweight and flexible. It can be stapled, taped, or battened into place.
- Multi-purpose – acts as vapour control layer, thermal insulation, and sometimes even a radiant barrier.
- Durable and long-lasting – water-resistant, mould-resistant, and resistant to pests.
This material is appropriate for small spaces and areas.
The cons of this material are:
- Low R-value by itself – alone, multifoil provides low actual thermal resistance — often R 0.8 to R 1.5.
- Needs careful detailing – performance depends heavily on correct installation with unventilated air gaps.
- Not enough as sole insulation – cannot meet Irish attic insulation standards alone.
Some brands exaggerate performance or suggest equivalency to 100 mm+ of traditional insulation — which is not accurate without specific conditions.
Which Material is Best for Ireland – Verdict
Based on all the topics we’ve covered above, there are two winners – the blown-in cellulose and the sheep’s wool.
Blown-in cellulose is the overall cost-to-performance winner. It’s cheaper than sheep’s wool and has very good R-value.
Sheep’s wool is best for the moist climate, especially if you live near the sea. It actively buffers humidity, but can be expensive.
There’s no one-size-fits all solution, so doing thorough research for your attic insulation project is required.
Tips on Future-Proofing Your Attic Against Fire and Noise
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The things you have to consider in the project are fire safety and noise reduction.
Fire safety is crucial for your property, because a small spark can cause a big fire if the whole attic insulation isn’t fire resistant.
Our tips for the fire safety of your attic are:
- Choose fire-resistant insulation – avoid flammable materials like untreated cellulose or low-grade foam without fire retardants.
- Use fire-rated plasterboard under rafters – meets Irish building code for fire resistance and slows the spread of flames.
- Seal electrical penetrations – never bury electrical connections in insulation, use proper junction boxes.
If your attic is a liveable space, you have to make sure that the insulation is also beneficial for soundproofing.
Our tips on soundproofing are:
- Opt for dense insulation – sheep’s wool, mineral wool, and dense cellulose are best for absorbing airborne noise.
- Use acoustic sealant – seal all gaps around floorboards, joists, sockets, and switches with flexible acoustic sealant.
- Add sound-reducing vent covers – use baffle boxes or acoustic covers on vents to prevent sound escape without blocking airflow.
Soundproofing your attic can also additionally increase the price of the property.
What Is the Cost of Insulating an Attic?
The cost of insulating an attic in Ireland varies depending on the type of insulation, the size and accessibility of the attic, and whether you go DIY or hire professionals.
A good example of a budget friendly option is a DIY fiberglass insulation. The materials only will cost around 700 to 900 euro.
On the other end is the sheep’s wool insulation. Materials alone can cost from 2400 euros up. If you decide to use professionals for the job, that will also add extra cost.
You can look at options for energy efficiency grants to help you with the costs.
Frequently Asked Questions
What is the most cost-effective attic insulation material?
Blown-in cellulose insulation offers the best cost-to-performance ratio for most Irish homes. It’s affordable, eco-friendly, fills all gaps, and has strong thermal performance.
Why is attic insulation so important for Irish homes?
The attic is one of the main places where heat escapes in winter and where hot air enters in summer. Proper insulation helps lower energy bills, regulates indoor temperature, and improves air quality.
Can attic insulation improve fire safety and reduce noise?
Yes. Certain insulation types, like mineral wool and sheep’s wool, are both fire-resistant and excellent at absorbing airborne noise.
