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BER Energy Assessments in Dublin, Ireland – Understanding Thermal Mass in BER Calculations

  • Mihai
  • 3 days ago
  • 3 min read
BER assessment showing wall construction layers and how thermal mass is calculated up to the first insulation layer

When carrying out a BER assessment for a dwelling or apartment in Dublin, Ireland, one of the most commonly misunderstood inputs is thermal mass.Correctly assessing thermal mass is essential for producing an accurate BER Certificate, and it is something every experienced BER assessor must handle carefully.

This article explains how thermal mass is assessed, what parts of the construction are considered, and why insulation location plays a critical role.


What Is Thermal Mass in a BER Assessment?

Thermal mass refers to a building’s ability to absorb, store, and release heat. In BER calculations, thermal mass influences:

  • Internal temperature stability

  • Heating demand

  • Overall energy performance rating

The BER methodology classifies thermal mass broadly as:

  • Light

  • Medium

  • Heavy

However, what actually counts as thermal mass is limited — and this is where many assumptions go wrong.


Key BER Rule: Thermal Mass Is Only Counted Up to the First Layer of Insulation

For BER purposes, only construction layers on the heated side of insulation are considered when determining thermal mass.

👉 Once insulation is reached, everything beyond it is excluded from the thermal mass calculation.

This rule applies to:

  • External walls

  • Internal walls

  • Ceilings and floors


Example 1: Internally Insulated External Wall

Consider a wall construction:

  • Gypsum plasterboard

  • Internal insulation

  • Concrete blockwork

  • External render

Even though concrete blockwork is a heavy material, it does not count in this case.

✔ For BER purposes:

  • The thermal mass calculation stops at the insulation

  • Only the gypsum board is considered

  • The wall is therefore classified as lightweight

This is a common scenario in retrofit projects and has a direct impact on the BER rating.


Example 2: Ceiling Construction in Apartments

In apartments, ceilings often consist of:

  • Gypsum plasterboard ceiling

  • 100 mm ceiling void

  • Concrete slab above (separating apartments)

In this case:

  • The ceiling void acts as a separation

  • The concrete slab above is not in direct thermal contact with the heated space

✔ For BER calculations:

  • The concrete slab is not considered

  • The ceiling is classified as lightweight

This applies even though the structure above is concrete.


Important Note: Concrete Slabs in BER Assessments

Within the BER methodology:

  • A concrete slab is always classified as medium thermal mass

  • It is never classified as heavy

This applies whether the slab is:

  • Ground-bearing

  • Part of an apartment structure

Understanding this avoids incorrect assumptions during BER data entry.


Why This Matters for BER Certificates

Incorrect thermal mass assumptions can lead to:

  • Overestimated energy performance

  • Non-compliant BER Certificates

  • Issues during SEAI grant checks

  • Issues during SEAI Audits

  • Inaccurate comparisons between properties

A qualified BER assessor in Dublin will always:

  • Review construction layers carefully

  • Identify insulation location

  • Apply thermal mass rules correctly


Final Thoughts

Thermal mass is not about what the building is made of, but what the heated space can actually interact with.

For accurate BER assessments in Dublin, Ireland, insulation placement, ceiling voids, and construction sequencing must always be correctly interpreted.

If you need a professional BER certificate, advice on upgrades, or support with SEAI grants, a qualified BER assessor makes all the difference.


BER Assessments Across Dublin and North County Dublin

We provide BER assessments and BER certificates across:

Dublin, Malahide, Portmarnock, Swords, Donabate, Lusk, Rush, Skerries, Balbriggan, Garristown, Ballyboughal, Naul, Oldtown, Loughshinny, Clontarf, Fairview, Marino, East Wall, Dollymount, North Strand, Raheny, Kilbarrack, Harmonstown, Edenmore, Donaghmede, Coolock, Artane, Whitehall, Santry, Drumcondra, Beaumont, Glasnevin, Griffith Avenue, Finglas, Ballymun, Dubber, Charlestown, Baldoyle, Bayside, Sutton, Howth, Ballsbridge, Donnybrook, Sandymount, Irishtown, Ringsend, Ranelagh, Rathmines, Rathgar, Harold's Cross, Terenure, Templeogue, Kimmage, Crumlin, Drimnagh, Walkinstown, Perrystown, Greenhills, Tallaght, Firhouse, Knocklyon, Ballycullen, Ballyboden, Whitechurch, Dundrum, Churchtown, Milltown, Clonskeagh, Goatstown, Stillorgan, Mount Merrion, Sandyford, Leopardstown, Ballinteer, Rathfarnham, Nutgrove, Blackrock, Booterstown, Monkstown, Deansgrange, Foxrock, Cabinteely, Cornelscourt, Killiney, Dalkey, Glenageary, Sallynoggin, Dún Laoghaire, Shankill, Loughlinstown, Ballybrack, Carrickmines, Stepaside, Ticknock, Kilternan, Enniskerry.


📢 Need Help with Your BER Assessment?

At MTS DNC Energy Consultants Limited, we provide accurate and up-to-date BER assessments based on the latest SEAI standards. Whether you're renovating, building, or just curious about how your current building ranks, we’re here to help.

📞 Contact us today for expert advice and a tailored assessment.





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