Solar & Daylight Data
Solar Shading Design: Letterkenny, Ireland
How to research solar shading design for a specific site in Letterkenny — the controlling authority, source documents, and checks to run before you rely on a number.
Last updated September 2, 2026 · Location data from the [GeoNames IE dump](https://download.geonames.org/export/dump/IE.zip) (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 2962961). Regulatory starting point: [Department of Housing, Local Government and Heritage and the local building-control authority](https://www.gov.ie/en/department-of-housing-local-government-and-heritage/collections/building-standards/). Figures are illustrative — verify against the current locally adopted edition for the site. Solar-method context: [NOAA Solar Calculation Details](https://gml.noaa.gov/grad/solcalc/calcdetails.html); the Harth monthly table uses a simpler declination and geometric-daylight approximation whose stated limitations must be retained. Project-date refinement reference: [NREL Solar Position Algorithm](https://midcdmz.nrel.gov/spa/).
Direct answer
For Letterkenny at 54.9500, -7.7333, the declination-only solar-noon altitude is approximately 58.5° at the June solstice, 35.0° at an equinox and 11.6° at the December solstice. Refine these geometry checks with the project date, civil time, facade azimuth, terrain and local horizon. The reproducible location record is GeoNames ID 2962961 in administrative area U, at 54.9500, -7.7333; replace it with the surveyed parcel point before relying on the result. As a transparent geometry check, declination-only solar-noon altitude is about 58.5° at the June solstice, 35.0° at an equinox and 11.6° at the December solstice. Representative 21st-day geometry ranges from about 6.9 hours in December to 17.1 hours in June; this excludes atmospheric refraction, terrain and obstruction effects. The cited national authority is a discovery starting point; current local documents and a named qualified reviewer control project use of this solar shading design record.
Prepared by Harth · Topic-specific calculated asset and fresh SERP brief passed editorial screening; page remains noindex pending the independent content, evidence, similarity and link gates · Published 2026-08-26 · Updated 2026-09-02.
What must be verified for Letterkenny?
Letterkenny is represented here at approximately 54.9500, -7.7333 for discovery and workflow planning. A project address, parcel, elevation, exposure, authority, and submission date must replace that city-centre reference before design use.
How should solar shading design be established?
- Fix the surveyed site and local time basis.
- Select an authoritative weather source or a named solar-position algorithm.
- Record period, percentile or scenario and units.
- Test sensitivity to elevation, exposure, urban form and horizon.
- Save the source file, retrieval date and checker in the model record.
| Input | Project-specific evidence | QA question |
|---|---|---|
| Site | surveyed coordinates, elevation and horizon | Does the point represent the building? |
| Weather/solar method | named dataset, algorithm, period and time basis | Are station, time zone and units explicit? |
| Design scenario | current and future scenario agreed by the team | Is an average being mistaken for an extreme? |
| Compliance | adopted local document and edition | Was applicability confirmed with the authority? |
What are the limits of this worksheet?
This shading-workflow page is a project-starting worksheet, not a design value or approval. The controlling authority and qualified professionals for the Letterkenny site remain authoritative.
Letterkenny horizontal-overhang screening worksheet
| Representative date | 09:00 altitude / P:H | Solar noon altitude / P:H | 15:00 altitude / P:H |
|---|---|---|---|
| 21 January | 5.71° / 10.009 | 14.91° / 3.755 | 5.71° / 10.009 |
| 21 February | 13.82° / 4.064 | 23.82° / 2.265 | 13.82° / 4.064 |
| 21 March | 23.60° / 2.289 | 34.65° / 1.447 | 23.60° / 2.289 |
| 21 April | 34.20° / 1.471 | 46.63° / 0.945 | 34.20° / 1.471 |
| 21 May | 41.54° / 1.129 | 55.19° / 0.695 | 41.54° / 1.129 |
| 21 June | 44.29° / 1.025 | 58.50° / 0.613 | 44.29° / 1.025 |
| 21 July | 41.79° / 1.119 | 55.49° / 0.687 | 41.79° / 1.119 |
| 21 August | 34.36° / 1.463 | 46.80° / 0.939 | 34.36° / 1.463 |
| 21 September | 23.78° / 2.270 | 34.85° / 1.436 | 23.78° / 2.270 |
| 21 October | 13.34° / 4.216 | 23.30° / 2.322 | 13.34° / 4.216 |
| 21 November | 5.43° / 10.524 | 14.61° / 3.837 | 5.43° / 10.524 |
| 21 December | 2.68° / 21.359 | 11.60° / 4.872 | 2.68° / 21.359 |
Letterkenny overhang sizing hand check
P:H is projection depth divided by the vertical facade distance to shade, calculated as 1 / tan(solar altitude). For a 1.20 m vertical target, multiply the table ratio by 1.20 m. The 09:00 and 15:00 columns use apparent solar time and show the solar-profile-plane ratio; they do not resolve facade azimuth, horizontal shadow displacement or a side-fin geometry.
The Letterkenny worksheet uses latitude 54.9500° and records longitude -7.7333°. A project study must replace the reference point, use the actual facade normal and obstruction mask, convert to civil time, test the full occupied period and account for diffuse sky, glazing and thermal performance. Refine solar positions with the NREL SPA.
Where can you explore related guidance?
- Explore all solar data guidance
- Sun Path: Letterkenny, Ireland
- Solar Altitude & Azimuth: Letterkenny, Ireland
- Daylight & Orientation: Letterkenny, Ireland
- Solar Shading Design: Sligo, Ireland
- All solar & daylight data guidance for Ireland
- Climate Design Data: Letterkenny, Ireland
Sources and method
Location data from the GeoNames IE dump (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 2962961). Regulatory starting point: Department of Housing, Local Government and Heritage and the local building-control authority. Figures are illustrative — verify against the current locally adopted edition for the site. Solar-method context: NOAA Solar Calculation Details; the Harth monthly table uses a simpler declination and geometric-daylight approximation whose stated limitations must be retained. Project-date refinement reference: NREL Solar Position Algorithm.
Source links
Frequently asked questions
What does the solar shading design record for Letterkenny establish?
The solar shading design record for Letterkenny establishes a reproducible discovery point at 54.9500, -7.7333 (GeoNames ID 2962961, administrative area U) and a Ireland source path. It does not establish a final project value, approval or parcel decision.
What must be replaced before using this solar shading design workflow for a project in Letterkenny?
For the solar shading design record in Letterkenny, replace the 54.9500, -7.7333 city reference with the surveyed site or parcel, identify the competent local authority, and verify the current documents under Building Regulations and Technical Guidance Documents. Record the edition, retrieval date, units, assumptions and named checker before relying on the result.
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