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Solar & Daylight Data

Updated 2026-09-02

Daylight & Orientation: Mtwapa, Kenya

How to research daylight & orientation for a specific site in Mtwapa — 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 KE dump](https://download.geonames.org/export/dump/KE.zip) (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 11002530). Regulatory starting point: [National Construction Authority and the applicable county government](https://www.nca.go.ke/). 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 Mtwapa at -3.9394, 39.7488, the declination-only solar-noon altitude is approximately 62.6° at the June solstice, 86.1° at an equinox and 70.5° 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 11002530 in administrative area 23, at -3.9394, 39.7488; replace it with the surveyed parcel point before relying on the result. As a transparent geometry check, declination-only solar-noon altitude is about 62.6° at the June solstice, 86.1° at an equinox and 70.5° at the December solstice. Representative 21st-day geometry ranges from about 11.8 hours in June to 12.2 hours in December; 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 Mtwapa?

Mtwapa is represented here at approximately -3.9394, 39.7488 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 Mtwapa site remain authoritative.

Mtwapa monthly daylight-orientation ledger

Representative dateGeometric daylightSolar sunriseSolar sunsetSunrise hour angleNoon bearingChange from prior month
21 January12.193 h05.9018.1091.45°180.0°-0.035 h
21 February12.104 h05.9518.0590.78°180.0°-0.089 h
21 March12.004 h06.0018.0090.03°0.0°-0.101 h
21 April11.892 h06.0517.9589.19°0.0°-0.111 h
21 May11.807 h06.1017.9088.55°0.0°-0.085 h
21 June11.772 h06.1117.8988.29°0.0°-0.035 h
21 July11.804 h06.1017.9088.53°0.0°+0.032 h
21 August11.891 h06.0517.9589.18°0.0°+0.087 h
21 September12.002 h06.0018.0090.01°0.0°+0.111 h
21 October12.109 h05.9518.0590.82°180.0°+0.108 h
21 November12.196 h05.9018.1091.47°180.0°+0.087 h
21 December12.228 h05.8918.1191.71°180.0°+0.032 h

Orientation checks prompted by the Mtwapa ledger

The representative daylight span runs from 11.772 hours on 21 June to 12.228 hours on 21 December. 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 Mtwapa at -3.9394°, 39.7488°, 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 KE dump (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 11002530). Regulatory starting point: National Construction Authority and the applicable county government. 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 Mtwapa establish?

The daylight and building orientation record for Mtwapa establishes a reproducible discovery point at -3.9394, 39.7488 (GeoNames ID 11002530, administrative area 23) and a Kenya 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 Mtwapa?

For the daylight and building orientation record in Mtwapa, replace the -3.9394, 39.7488 city reference with the surveyed site or parcel, identify the competent local authority, and verify the current documents under National Building Code and county development-control requirements. Record the edition, retrieval date, units, assumptions and named checker before relying on the result.

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