Irish guidance for replacing windows and doors
Window and door replacement plan
Approach an external-door or window upgrade by reading the property first; finishes, ironmongery and handing come later. Correct dimensions alone do not make a unit appropriate. The perimeter detail may be unresolved, an opening leaf could foul a radiator or walkway, and extra glazing may need structural review. Identify the Irish guidance that fits the building and the nature of the alteration. Take dependable measurements, photograph the setting, and discuss technical points early with suitably competent design and installation professionals. The sections below distinguish choosing the unit from assessing energy performance, detailing the installation and completing the checks that matter for work in the Republic of Ireland.
01 / Survey the building
Describe the work as one project
Avoid reducing the brief to “replace ten windows”. List the affected openings, state whether their dimensions will change, and identify related work to shutters, cills or facade finishes. Record whether each door serves the main entrance, a patio or secondary access. Give every opening its own survey sheet with interior and exterior views, clear dimensions, wall depth, sill level, hinge position and images of the frame, reveal and threshold. Add visible damage, damp indications, irregular surfaces, radiators, furniture and external shading. The resulting record gives designers and specialist contractors a brief they can inspect and price.
Distinguish a like-for-like unit in the current aperture from work that alters the building. Converting a small window to a near-floor-level door, deleting a fanlight or enlarging the aperture goes beyond substituting one element. A new side light, changed threshold or different outer finish can also turn an apparently simple entrance door into a design task. Decide the appearance and required movement area at the outset. If the proposed leaf swings away from the room, an external door with an outward swing is a product option; suitability of the particular opening, outside space and wall junction must be assessed independently of the product title.
Put Irish energy guidance in context
For existing dwellings, Technical Guidance Document L 2022 expressly considers replacement external doors, windows and rooflights. Its guidance gives an average U-value for replacement units of no more than 1.4 W/(m²K). The right Part L edition and route depend on the project, especially where the work is not a straightforward replacement in a dwelling. The value should not be applied indiscriminately to every building. Ventilation, secondary escape and heritage considerations also remain relevant, as described in TGD L 2022.
The quoted U-value relates to the complete element on the basis stated by its supplier; it cannot describe the entire alteration. Confirm the dimensions and specification used for the calculation and obtain documentation for the ordered configuration. In a wide aperture, changing the balance of frame and glass may affect performance. A door with fixed side lights and moving sections may also need careful specification. An outward-opening Super Low Uw passive-house window identifies a particular product arrangement, but neither certifies its use in every home nor proves compliance for a specific job. Base the required performance on the project's assessment and documented specification.
02 / Classify the elements
Do not assume an exemption
Irish guidance treats repair of separate components differently from replacement work. Determine how the proposal is classified from the building, element and scope involved; do not presume that limited work falls outside the relevant requirements. The distinction is set out in TGD L 2022. For several openings, schedule both the current units and the proposed replacements, including exterior dimensions and purpose. State whether the works form one phase or several, and record connected alterations that could influence professional advice. Mark each aperture on an elevation with its own code, then repeat that code on the survey record, photographs and quotation. This provides a traceable assessment trail and reduces mistakes between similar-looking units.
Treat the assessment as an early project task, not a calculation added after product selection. Keep the opening schedule, dimensions, element types, photographs and quotations together so an energy adviser or designer can understand the proposed sequence. A potentially available compliance route is not a reason to disregard better thermal performance. Comfort, sound reduction, operation, appearance and the risk of condensation around the perimeter remain separate considerations. Equally, an impressive U-value cannot compensate for installing into a damp, damaged or distorted reveal. For an apartment, obtain the lease and ask the owner-management company to confirm its position on exterior and common elements before settling the specification. Record who reviewed each point and resolve uncertainties before authorising manufacture.
Do not confuse windows, patio doors and external doors
Informal names are often ambiguous, so define each element by what it must do. A window provides light, outlook and ventilation and may need to open for cleaning. A patio door links the room with an exterior area and must work with circulation, furniture and the threshold. The main entrance introduces further questions about access, security, side lights and a canopy. Irish dwelling guidance addresses replacement windows, rooflights and external doors, while ventilation and secondary escape functions must also be considered. These matters are covered in TGD L 2022. Describe what the door must do, rather than asking only for a “glazed door”.
A common problem arises where an existing patio door opens inwards but a sofa, dining table or radiator will sit closer to the opening. Opening direction then determines usable space. A one-leaf patio door opening inwards makes sense where the leaf is intended to enter the room, while an outward-swinging version uses a different area. Plot the full arc on a scaled sketch or mark it physically on the floor before deciding. Check the route to the garden, curtain positions and likely use during windy or wet weather. Allow for someone passing through with shopping, tools or other bulky objects.
03 / Plan the junction
Include the wall connection in the specification
Performance depends on how the new unit meets the fabric. Design the frame fixing, seals, insulated reveal, interior and exterior perimeter treatments, and the cill or threshold as a coordinated detail. Give the installer information about the wall build-up, masonry condition and existing moisture barriers, and establish whether removal includes the complete existing frame. Opening up an older home may reveal decay, cavities or distorted surfaces that change the planned sequence. Pre-removal photographs support the record, but a competent inspection at the property is still necessary.
Make the quotation answer practical questions. Define the removal work, preparation of the perimeter and the allowance for unsound background material. State which decisions must wait until the opening is exposed. Allocate responsibility for plastering, exterior finishes, cills, sealing and any shading system. Confirm whether manufacture will use the structural aperture, a survey dimension or a finished unit size. A window with a fixed glazed light can reduce operating requirements compared with a movable sash, yet the perimeter still needs design. Cleaning access, daylight and the wall construction remain relevant to a fixed light. Record the installation method and allocated responsibilities in the project papers instead of relying on a conversation.
Plan ventilation consciously after replacement
New units generally leak less air than old draughty frames, changing how the rooms exchange air. No single technical response follows in every case, but moisture from cooking, showers, clothes drying and occupation still needs a dependable route out. Examine the ventilation pattern across the home or apartment, not aperture by aperture. Bedrooms, seldom-used spaces and high-humidity rooms behave differently through the day. Position also determines whether opening windows on opposite sides is realistic and whether the intended routine will work.
Let an appropriately competent installer or designer decide what ventilation review the particular building and works require. Product selection should answer three practical questions: which units are operable, whether their controls are accessible, and during what conditions they may remain open. A top-hung casement with an outward opening can work differently at high level from a side-hung unit close to the floor. Opening style alone is not a ventilation plan. Run through real routines: airing a bedroom in the morning, clearing moisture after a shower, cooking and leaving the property unattended. A proposal dependent on continuous occupant intervention may be unsuitable. Write down the expected routine and identify who will explain it at handover. Before ordering, consider whether road noise, security needs, fly screens, driving rain or exposure will limit the periods when windows can remain open.
04 / Release the order
Check rooflights and special shapes separately
A rooflight occupies the roof slope rather than the vertical facade. Coordinate the selected unit with the roof construction, weathering layer, internal lining, reveals and safe access for fitting and maintenance. Irish dwelling guidance includes replacement rooflights and states an average replacement-unit U-value of no more than 1.4 W/(m²K). Measure and specify rooflights separately from facade units. Provide the roof pitch, covering, interior finish and intended opening method.
Unusual geometry makes an accurate survey of the aperture particularly important. Circular work, triangular heads and inclined edges may suit the existing architecture, but they demand dependable templates, dimensions and details of the surrounding support. A fixed glazed triangular and sloping window can suit a non-rectangular aperture, although the product description alone establishes neither dimensions nor structural compatibility. Ask the supplier which sight sizes, angles, diagonals and reference lines are required. Width and height by themselves are rarely adequate for an asymmetric form. Clearly label datum edges, the room face, the exterior face and the apex. Record any bowing or deviation instead of assuming straight sides. Check a scaled approval drawing against the completed survey before manufacture. The design must also settle the internal finish and route for water outside. Seeking additional daylight should not leave roof weathering or adjoining cladding without a resolved detail.
Choose large openings around use and construction
A generous garden-facing glazed area changes circulation and construction as well as outlook. Consider furniture, the path through the room, clearance around open panels, the threshold, floor layers and adjoining paving. Folding leaves need a defined stacking position. Sliding and lift-and-slide panels remain on their tracks, although the division between fixed and moving sections controls the clear route and view. Assess the selected system against the actual building, including exposure, drainage and threshold weathering. Relevant dwelling energy guidance is found in TGD L 2022. Ask a competent professional to consider the applicable category and requirements.
Judge the layouts through ordinary routines, not only by their widest opening. Locate the dining table, decide whether a buggy, trays or garden tools must pass, identify the usual operating side and plan safe access for cleaning. A Patio Life sliding-and-lifting door can enter the comparison when sideways movement is preferred. A folding arrangement may serve a scheme where opening almost the full width is the priority. Draw the fixed and moving panels for both, including the space needed for operation and stacking. Compare quick garden access, a fully open setting for visitors, ventilation during changeable weather and cleaning of the outside glass. This exercise shows which arrangement offers the more useful daily compromise. Either choice needs a properly designed threshold and drainage route coordinated across the room floor and outdoor paving. Resolve those interfaces before manufacture rather than treating them as finishing details.
05 / Document installation
Discuss appearance early
Older homes often derive much of their appearance from glazing divisions, frame proportions, position and the way their windows open. Existing details need not always be copied, but the visual objective should be settled ahead of product configuration. Decide whether the elevation should become simpler, whether established divisions should continue, or whether a broad modern pane is intended. Take photographs of the complete facade from far enough away to show its composition. Those views allow the proposed unit to be considered alongside the other openings, entrance and roof instead of as an isolated product.
If conservation, protected-structure or planning concerns are possible, contact the planning authority for the property's location before approving final dimensions or appearance. Nothing here amounts to permission for a particular Irish building. Product terminology also needs care: a decorative bar applied to glazing differs visually and structurally from a bar that separates panes. An traditional “Kombi” casement opening outwards can help express the intended traditional appearance, without establishing that the proposal will be accepted for the property. Share elevations, site photographs and design priorities with the professionals and supplier before technical sign-off.
From checks to a reliable order
Final approval needs substantially more detail than a count and finish. For each unit, verify overall dimensions and their datum, width, height, handing from the room side, leaf count, fixed lights, handle position, glazing divisions and glass specification. For a door, also document the usable passage, threshold detail and relationship with the exterior area. Request declared performance for the unit as configured and have the Irish requirements checked against the building and project scope. A catalogue U-value informs that review but cannot by itself demonstrate a compliant installation under TGD L 2022.
Set out the sequence and name the person responsible for surveying, dimensional approval, inspection of the fabric, installation and completion of both perimeter faces. Agree how concealed defects and departures from the drawings will be photographed, reported and authorised. Retain the quotation, approved drawings, product data, measurement sheets, before-and-after images and handover papers in one file. Bloomcabin's commercial guarantee for windows and doors is 5 years, and delivery takes 4–6 weeks subject to order confirmation. Do not commit removal or follow-on trades until that confirmation arrives. An organised record also supports maintenance, queries and an evidence-based handover.
Common questions
Must every replacement window achieve a particular U-value?
Not without assessing the particular case. TGD L 2022 gives an average replacement-unit U-value of no more than 1.4 W/(m²K) for replacement external doors, windows and rooflights in dwelling guidance. A professional should identify the relevant Part L edition, building type, scope and compliance route. The source is TGD L 2022.
Do entrance doors have the same value as windows?
Not automatically. Irish dwelling guidance groups replacement external doors, windows and rooflights under average replacement-unit guidance of no more than 1.4 W/(m²K), though the building, product and compliance route still require project-specific assessment. The figure should not be extended to every type of work.
Can the existing frame alone be measured for an order?
Not always. Ask the supplier which reference dimensions are needed and establish how removal, fixing and perimeter seals are to be handled. Along with height and width, capture the wall depth, reveal condition, threshold and irregularities. The specialist responsible for the survey should confirm the manufacturing dimensions.
Should windows and patio doors be specified together?
They may differ visually, but their technical design often overlaps. Both influence the elevation, airtightness, perimeter construction and potentially the energy assessment. A patio door adds circulation, threshold and outdoor-surface issues. Coordinate the openings on each facade and identify which are fixed, operable or used for access.
Will improved airtightness always mean mechanical ventilation?
No automatic answer is reliable. Replacement changes air leakage, so assess moisture generation, occupancy patterns, room arrangement and existing ventilation together. A competent building professional should establish whether this property and the proposed scope need a ventilation assessment or further measures.
Next step
The most consequential choices for a window or door upgrade occur ahead of purchase: define the alteration, classify each element, establish the relevant Irish guidance and design its connection with the existing fabric. For applicable dwelling replacements, the average 1.4 W/(m²K) guidance is one important check, not a substitute for measurement, ventilation review or coordinated wall and threshold details. Survey every aperture, test the handing against the actual room layout and authorise dimensions only after the product and installation responsibilities agree. Careful preparation makes the work traceable from initial survey through fitting and handover.
Sources
Checked 16.09.2026 2026-09-16
- Technical Guidance Document L 2022 — Conservation of Fuel and Energy — Dwellings — Republic of Ireland
- Technical Guidance Document L 2022 — replacement windows, doors and rooflights — Republic of Ireland
