The Lintel Is a Radiator You Cannot See

The wall is cream. The WhatsApp photograph is eaves to damp-proof course, and someone in the group chat has written “class”. Put a hand on the plaster a metre from the glass and the house feels finished. Put a hand on the plaster immediately above the pane and you have found a radiator you cannot see.

That radiator is not the window. The window is glass in a hole. That radiator is the beam that holds the bricks up over the hole. Builders call it a lintel. Heat calls it a shortcut.

The beam that holds the bricks up

Let us invent a person. We will call her Eileen. 1964 semi, Marino. Yellow brick, a cavity filled whenever that was, later a cream wrap. The sitting room is “grand now” except for a black ruler along the top of every window, the one she wipes in March and that comes back in November like a subscription she never signed.

The jambs are not the story. The cill is not the story. The field of the wall is fine. That is the insult. The cold lives in a strip the width of a beam, immediately over the glass, where a dense concrete lintel — or a steel one — sits like a letterbox for heat.

A lintel is not a decoration. A lintel is a structural sentence: something has to carry the masonry above the hole, so you put a beam there. In a Dublin house that beam is usually precast concrete, heavy as a pavement slab, or a steel box spanning the inner leaf, the cavity, and the outer leaf in one piece of metal. Concrete conducts. Steel conducts as if conduction were a sport.

Heat walks through the beam

Insulation is a fence. Heat is a toddler. The toddler does not argue with the fence. The toddler walks to the gate. On a Dublin elevation the obvious gates are the openings. The less obvious gate is the beam over the opening: a lump of dense stuff connecting the warm side of the house to the weather.

U-value is the score for the field: how easily heat walks through a square metre of wall. Psi-value is the score for the line: how easily heat walks along the junction. A beautiful U-value with a rude lintel is a jumper with a metal zip that ends in the rain. You will still be cold at the zip.

Researchers at UCL built a paper around an uninsulated lintel detail and found the unromantic thing: leaving the lintel uninsulated made the thermal bridge “unacceptable” for mould risk in every window position they tried. They were looking at internal lining. The toddler does not care which side of the wall the fence is on. Leave the beam naked and the house keeps a radiator over every pane.

This is not a plastered window reveal, a stuffed air brick, or a party wall dumping heat into next door. Those are other holes, and they have had their Saturdays. This hole is a beam. It is dry, wrapped or filled, photographically complete, and still a radiator at the head of the glass.

Two costumes, same beam

There are two costumes in Dublin, and they fail the same exam.

Costume one: cavity fill. Two leaves, a gap, a hopper, a weather of beads. The gap is the job. The lintel is not the gap. A steel box lintel sits in that gap on purpose, tying the leaves together over the hole. Fill the gap and the field improves. The beam is still a motorway through the beads. An insulated or thermally broken lintel exists. A lot of the ones in 1964 Marino do not.

Costume two: the wrap. Boards on the outer face. Render. A cream house. External wall insulation Dublin as a weather coat, not a paint job. The coat is correct for the field. The coat is a lie at the head if the boards stop at the brick and leave the beam in the weather. The 2021 Acceptable Construction Details for external wall insulation draw the continuation: insulation running over the lintel and returning to the frame at the head. Jobs skip it because the brick looks finished and “sure it’s only the lintel.” The lintel is the point.

The second-wall ticket in 2026 is how a 2014 hopper and a 2026 wrap end up on the same house. If you already used the cavity grant, you can still talk about a wrap. The wrap is not a spell that makes the beam disappear. Cover the lintel or you own two certificates and the same black ruler.

The live piece on the window reveal that is a radiator is a different hole: the picture frame around the glass. Do not confuse a missing cuff with a missing beam. You can insulate the jambs and still dump heat through a concrete bar sitting on top of them. They are not the same job.

The black ruler is physics

Mould is not a lifestyle. Mould is a surface that got cold enough, long enough, in a room that makes water the way people make water: showers, kettles, sleeping. The field of an insulated wall stays above the trouble. An uninsulated lintel drops. Indoor air hits the plaster under the beam, drops its drink, and the head of the window starts a hobby.

Eileen wipes. She replaces the window because a man said the glass was the problem. The new window sits under the same beam. The stripe takes a month off and comes back. The wall is still “done”. The lintel is still a radiator.

You can feel it without a camera. The plaster a hand’s width above the glass is a different temperature to the plaster in the middle of the wall. That difference is the quote that stopped at the brick.

What the camera is looking for

You cannot diagnose a lintel from the footpath. The cream coat looks finished. Finished is a paint word.

A surveyor looks at the head. Is there insulation covering the outer face of the lintel and meeting the frame, or render on cold concrete, or a steel box flashing heat into the room? On a wrap: do the boards run over the lintel, or stop at the brick? On a cavity: is the lintel thermally broken, or a steel shortcut the beads were supposed to “sort”? A thermal camera is a beam-detector: the field is dark, every opening wears a glowing bar along the top. Guessing is how the lintel survived two grants.

If the person quoting you will not look at the heads, they are quoting a field. A field is not a house. A house is a field plus every beam over every hole.

The money, without folklore

These are the current individual-grant figures, taken from SEAI’s own wall page. They are fixed by house type, not a percentage of a quote, and they are not a prize for wrapping a field and leaving a radiator over every pane.

Cavity wall insulation, standard: apartment €700, mid-terrace €850, semi-detached or end-of-terrace €1,300, detached €1,800. That money is for a cavity that deserves a fill: clean, dry, empty. It is not a bounty for pumping the gap and ignoring the steel box that sits in it. Higher cavity figures exist if you are on a qualifying welfare payment: apartment €900, mid-terrace €1,100, semi-detached or end-of-terrace €1,700, detached €2,300.

The wrap is €3,000 for an apartment, €3,500 for a mid-terrace, €6,000 for a semi-detached or end-of-terrace, and €8,000 for a detached house. Internal lining is €1,500 / €2,000 / €3,500 / €4,500 across those same four types. The official wall numbers live on the SEAI wall insulation grant page. The plain-English table, edited 28 May 2026, lives on the Citizens Information page for Better Energy Homes.

Attic insulation is still the hat, and the hat still comes first. Standard: apartment €1,100, mid-terrace €1,400, semi-detached or end-of-terrace €1,500, detached €2,000. Enhanced, if you qualify: €1,400 / €1,800 / €1,900 / €2,500. What you pay after the grant, on a normal Dublin attic done properly, is typically €300 to €1,500. Do the hat. Then argue about the walls, including the beams.

The house has to have been built and occupied before 2011. Approval comes before work. If work starts before SEAI says yes, the grant is gone. If SEAI does not approve, no work starts, and you pay nothing. That is the grant guarantee as Retrofit Dublin runs it. Retrofit Dublin is SEAI-registered. The phone is 01-233-7477. The 15-year guarantee is on the insulation, not on the folklore that a cream elevation is a finished lintel.

Technical Guidance Document L is the energy rulebook: U-values for the field, and Appendix D for the lines, because a wall is not only a wall. A default y-value of 0.15 is the polite way of saying “we did not draw the junctions.” 0.08 is the number you get when the junctions look like the drawings. Lintels are in the drawings. The Irish Times set out the 2026 second-wall change when the package landed. RTÉ put the insulation-grant increases in the same January announcement. Neither of them is going to write you a hymn about a concrete bar over a window. That is our job.

Cover the beam, then argue about the coat

A whole-home energy strategy is an order of operations. You stop the leaks. Then you change how you make the heat. The cheapest first move in most Dublin houses is still the hat. Then the walls — including the beams over the glass. Cavity if the camera says the gap is clean, dry, empty, and the lintels are not a steel rumour. A wrap if the cavity is the wrong job, with the boards returned over every lintel so the coat does not stop at the brick. Then the machines.

Retrofit Dublin does home energy upgrades in that order on purpose: fabric, then systems. A heat pump behind a cream wall and a set of uninsulated lintels is a very efficient device heating the beams. Do not buy an expensive machine to feed a radiator you refused to cover.

You can keep the quote that treated the window heads as someone else’s invoice. The field can be fine. The beam can still be a radiator. Do the hat. Look at the heads. Return the insulation over the lintel. Apply before anyone drills. If SEAI does not approve, no work starts, pay nothing. Phone 01-233-7477.

If the lintel is still a radiator you cannot see and the cream coat still stops at the brick, call 01-233-7477 and Claim Your Grants.