Natural Daylight | GTH Architects

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Karl Taylor, founding director of BTR specialist GTH architects has provided a few insights into how natural daylight can be employed to deliver an enhanced well-being customer experience.

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Natural daylight and BTR

The providers of BTR products are highly attuned to the competitiveness of their marketplace. The smart players are laser-focused on the quality of experience their product provides for their customers and, to this end, each component of the customer experience is forensically interrogated to identify potential improvements that in turn improve competitiveness, even if, by the smallest of margins.

Being able to authentically promote wellbeing as a core attribute of a BTR offer plays to a ballooning customer expectation and – given the perceived importance of natural daylight in the wellbeing conversation - there are few more compelling ways in which this can be achieved than designing buildings from first principles optimise the use of natural daylight.

The benefits of natural daylight are multi-faceted, not least, its contribution to carbon reduction via the reduced need for artificial light and its contribution to passive energy for winter heating. The main impact of good daylighting in the home, however, is on the comfort and wellbeing of occupants - not to mention the simple fact that good quality natural light makes the interior of a home more pleasant and enjoyable to occupy.

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Distribution and Configuration of Building Components

BTR schemes generally require scale to deliver financial viability – typically starting at around 150 apartments. This inevitably gives rise to challenges for design teams when assessing how to achieve massing on sites – particularly within tight urban locations - whilst simultaneously optimising the penetration of natural daylight. Here it is crucial that we carefully consider:

The scale and proximity of building components in respect to one another so that they mitigate overshadowing (and overlooking) both within and without the development.
Ideally, apartments should be dual aspect, with rooms used in the morning, i.e. bedrooms and kitchens oriented to the eastern morning sun to stimulate our circadian rhythms.
Principle family rooms should have access to direct sunlight for at least 2 hours per day, year-round, preferably within creased views of the sky – particularly important in dense urban locations.
Despite the very powerful economic arguments to forgo on this, circulation corridors are infinitely more welcoming and enjoyable when pierced by natural light. There are always balance points between economics and quality but when customer retention is paramount, BTR ignores the quality argument at its peril.

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Fig 1: Illustrates the challenges of achieving density on tight urban sites, the twin block solution (left) results in overshadowing and overlooking whilst the single block solution (right) provides more opportunity for optimal conditions.

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Depth and heights

For the detailed design and provision of daylight in buildings, one should refer to the Europe-wide standard, BS EN 17037. However, there are several basic rules of thumb that evidence good quality daylight design within BTR apartments:

All habitable rooms (bedrooms, living rooms, kitchen-dining rooms) should be provided with areas of glazing that are equivalent to a minimum of 20 per cent of the rooms they serve.
Room depths should generally be less than 2.5 x the height of the head of the window.
Horizontal windows distribute daylight more uniformly across the space.
When used, vertical windows should be spread out across a wall rather than concentrated to achieve more even distribution of light.
Where possible, windows should be positioned on more than one wall - bilateral daylight is better than unilateral daylight for glare reduction and light distribution.
It is human nature to walk towards the light – at Geraghty Taylor, we capitalise on this primordial instinct to help navigation and orientation by placing windows at the ends of hallways and corridors.

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Illustrates how a shallower apartment layout receives greater penetration of natural daylight, (it should be noted, however, that the shallower plan also results in more external wall which can be more expensive and can potentially reduce the number of apartments that can be achieved on a given site. This is a serious balance point/consideration for a BTR developer, i.e. what strategy trumps what in the business model?). — Fig2: Illustrates how a shallower apartment layout receives greater penetration of natural daylight, (it should be noted, however, that the shallower plan also results in more external walls which can be more expensive and can potentially reduce the number of apartments that can be achieved on a given site. This is a serious balance point/consideration for a BTR developer, i.e. what strategy trumps what in the business model?).

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*Fig 3: ‘Walking towards the light’ – the incorporation of external views at the end of corridors positively enhances the experience of moving around our homes.*

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Personal Control

Personal control over the amount of incoming daylight provides welcome opportunities for the inhabitants of BTR homes to adjust the conditions of their apartments to suit their own patterns of use, resulting in a greater sense of agency over their environment (particularly important in a rental product) and by extension enhancing wellbeing:

Windows should offer a range of conditions, for example, light that is from above, the side, direct, diffuse and adjustable by shutters, louvres or blinds.
Bedrooms should have effective blackout options to support good sleep patterns and night-time privacy, again in the form of blinds or shutters.
Window cills, rather than floor to ceiling windows, allow BTR customers to combine the benefits of natural daylight with the ability to personalise and express themselves within their apartments with ornaments and personal effects - the occupier’s ‘stuff of life.

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