Francis Knows: Building Solar-Ready
Lessons Learned from Developing Whisper Valley in Austin, TX
"Providing an empty conduit from the main service panel to the largest southern roof surface – and if the service is indoors, providing an empty sleeve from the main service to the meter area outdoors – is typically all that need be done. Other common obstacles to consider during design are inadequate roof square footage, or cardinal orientation of the roof pitch, or a smattering of vents and skylights on the would-be solar roof surface."
Solar integration at the earliest phase of design is key to long-term solar adoption and affordability. The City of Austin’s resolve to ensure all homes are solar-ready is both forward-thinking and admirable - however it can present unique challenges. The message should focus on being effective and simple. The goal is to standardize and simplify builder implementation and to remove possible obstacles to homeowners’ retrofits through considerate design practices. This will allow for maximum affordability, and thus feasibility of solar-ready practices for all parties. Ultimately, simplifying communication and adoption of best-practices for builders ensures the removal of potential obstacles for homeowners considering a solar installation.
Traditional designers and builders need to be educated about the ease of incorporating solar-ready design - yet they are historically reticent to adopt new practices or technologies, especially if it would add to the cost of building. Importantly, the nuances to any ordinance or protocols need to maintain, ensure, and reiterate that minimal work and design consideration with no specialized equipment or costly design features need to be adopted – the parties will not have to perform any type of work that they aren’t already comfortable with, or even increase the price of their homes that are built solar-ready. Key points to illustrate should be that solar-ready integration involves simple processes relatable to a traditional scope of work when building a home – it uses the same conduits, same wires, same screws, same codes, and same practices they perform and install every day.
For example, simply providing an empty conduit from the main service panel to the largest southern roof surface – and if the service is indoors, providing an empty sleeve from the main service to the meter area outdoors – is typically all that need be done. Other common obstacles to consider during design are inadequate roof square footage, or cardinal orientation of the roof pitch, or a smattering of vents and skylights on the would-be solar roof surface. Additionally, installing inadequate building electrical service, or the need for costly and invasive retrofits that involve removing roof tiles or drywall for equipment installations can make a solar retrofit considerably more expensive. Choice of roofing material can also make a significant impact on the cost of a solar install. Tile roofs are the most expensive to retrofit solar panels on, while traditional asphalt shingle or metal roofs are the most cost effective.
Mitigating issues in home design is actually quite simple, and can be the sole determinant in whether a home is solar-ready, or even solar capable. An overarching design consideration is to provide adequate southern roof surface free from obstructions. A common roof surface sizing metric is that 100ft² can accommodate 1 kilowatt of solar. Generally, a modern, efficient home can accommodate a 5 kilowatt solar array. Therefore a minimum of 500ft² of southern facing roof pitch is often adequate. Also, keeping skylights and plumbing vents off of the southern pitch, or placing them within 3 feet of the roof peak is a best practice. Another design consideration is that most solar installations would do well to have two electrical conduits installed for the solar roof surface – one high voltage DC raceway and one low voltage communication raceway – to ensure future code compliance and system monitoring capabilities. Additionally, inadequate building electrical service can be a cost-prohibitive challenge when considering solar, so homes should be equipped with main service busbars and transformers capable of 200 amps or more. Lastly, a common industry metric worth further qualifying with local data is to say that 8 kilowatts of solar can power a 3000ft² home, therefore one pair of conduits per 3000ft² should ensure future system capacity availability.
In conclusion, making a home solar ready is quite simple. However, it is crucial that the conversation begin at the earliest stages of design and site layout, and be presented in a manner that lets all parties understand the simplicity of making a home solar ready.