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Solar & Daylight Data

Updated 2026-09-02

Daylight & Orientation: Douglas, Ireland

How to research daylight & orientation for a specific site in Douglas — the controlling authority, source documents, and checks to run before you rely on a number.

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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 2964690). 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 Douglas at 51.8744, -8.4350, the declination-only solar-noon altitude is approximately 61.6° at the June solstice, 38.1° at an equinox and 14.7° 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 2964690 in administrative area M, at 51.8744, -8.4350; replace it with the surveyed parcel point before relying on the result. As a transparent geometry check, declination-only solar-noon altitude is about 61.6° at the June solstice, 38.1° at an equinox and 14.7° at the December solstice. Representative 21st-day geometry ranges from about 7.5 hours in December to 16.5 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 daylight and building orientation 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 Douglas?

Douglas is represented here at approximately 51.8744, -8.4350 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 daylight and building orientation be established?

  1. Fix the surveyed site and local time basis.
  2. Select an authoritative weather source or a named solar-position algorithm.
  3. Record period, percentile or scenario and units.
  4. Test sensitivity to elevation, exposure, urban form and horizon.
  5. Save the source file, retrieval date and checker in the model record.
InputProject-specific evidenceQA question
Sitesurveyed coordinates, elevation and horizonDoes the point represent the building?
Weather/solar methodnamed dataset, algorithm, period and time basisAre station, time zone and units explicit?
Design scenariocurrent and future scenario agreed by the teamIs an average being mistaken for an extreme?
Complianceadopted local document and editionWas applicability confirmed with the authority?

What are the limits of this worksheet?

This daylight-workflow page is a project-starting worksheet, not a design value or approval. The controlling authority and qualified professionals for the Douglas site remain authoritative.

Douglas monthly daylight-orientation ledger

Representative dateGeometric daylightSolar sunriseSolar sunsetSunrise hour angleNoon bearingChange from prior month
21 January8.286 h07.8616.1462.14°180.0°+0.760 h
21 February10.047 h06.9817.0275.35°180.0°+1.761 h
21 March11.931 h06.0317.9789.49°180.0°+1.885 h
21 April14.018 h04.9919.01105.13°180.0°+2.086 h
21 May15.714 h04.1419.86117.86°180.0°+1.696 h
21 June16.474 h03.7620.24123.55°180.0°+0.760 h
21 July15.780 h04.1119.89118.35°180.0°-0.693 h
21 August14.050 h04.9819.02105.37°180.0°-1.731 h
21 September11.966 h06.0217.9889.74°180.0°-2.084 h
21 October9.950 h07.0216.9874.63°180.0°-2.016 h
21 November8.220 h07.8916.1161.65°180.0°-1.731 h
21 December7.526 h08.2415.7656.45°180.0°-0.693 h

Orientation checks prompted by the Douglas ledger

The representative daylight span runs from 7.526 hours on 21 December to 16.474 hours on 21 June. Solar sunrise and sunset are expressed in apparent solar time, not a time-zone clock. The noon-bearing column is a true-north azimuth screen and becomes unstable when the sun passes close to zenith.

For Douglas at 51.8744°, -8.4350°, test each occupied facade against the actual horizon, adjacent buildings, glazing, room depth and target illuminance. This ledger describes geometric availability only; it does not estimate irradiance, daylight autonomy, glare or energy. Refine project-date positions with the NREL SPA.

Where can you explore related guidance?

Sources and method

Location data from the GeoNames IE dump (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 2964690). 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 daylight and building orientation record for Douglas establish?

The daylight and building orientation record for Douglas establishes a reproducible discovery point at 51.8744, -8.4350 (GeoNames ID 2964690, administrative area M) and a Ireland source path. It does not establish a final project value, approval or parcel decision.

What must be replaced before using this daylight and building orientation workflow for a project in Douglas?

For the daylight and building orientation record in Douglas, replace the 51.8744, -8.4350 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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