There are two legitimate ways to satisfy Title 24. One is a fixed list you either meet or you do not, quick and cheap to document. The other models your building and buys back design freedom. This tells you which one your project is heading for.
Nothing here is a quote, a bid, an engineering determination or a boundary determination. We are a drafting and design firm: we coordinate with a licensed structural engineer and a Licensed Land Surveyor when your project needs one, rather than performing or stamping that work ourselves.
Prescriptive is a checklist. Title 24 publishes minimum values for your climate zone — how much insulation goes in the walls and ceilings, what the glazing has to perform at, what the ducts need, how the water is heated — and meeting every line on that list is compliance. Nothing trades against anything else. Miss one item and the package fails however far you exceeded the rest. What you get in return is something quick to produce, cheap, and easy for a reviewer to verify.
Performance is a simulation. The software runs a full year of energy use on the building you actually designed and weighs it against a notional twin of identical size and shape assembled to the prescriptive minimums. Land at or under that benchmark and you comply, regardless of which combination got you there. Surplus glass is paid for elsewhere — sharper glazing, deeper insulation, a heat pump, ducts that leak less, generation on the roof.
Neither route carries more legitimacy than the other. Nobody should read performance as a workaround, or as damage control after a design fails. It is simply where most current residential architecture lands, since open plans, wide sliders and vaulted ceilings were never the sort of building a fixed checklist was written around.
This is the part that surprises people. Choosing a compliance route is not just a paperwork decision — it determines what has to appear on the drawings and how firmly.
On the prescriptive route, the sheets carry the usual package: R-values called out through the sections, a fenestration schedule listing performance against each unit, notes covering how the ducts are sealed and tested, and the mandatory measures sheet. Predictable, and those figures seldom shift once fixed.
On the performance route, the simulation writes the specification and that specification binds. If passing depended on U-0.28 glazing, the schedule reads U-0.28 and the units delivered to site have to match. Substitute something cheaper mid-construction and the compliance breaks, which surfaces at final inspection. The same is true of insulation, duct routing, how efficient the equipment is, and any rooftop generation the run counted on.
Which is the argument for producing report and sheets in one place, rather than buying them from two firms that never speak. We handle Title 24 CF1R energy calculations alongside the permit set, so the assumptions inside the simulation are the same ones printed on the drawings and installed on site.
Not intrinsically. Reviewers see it constantly, and it is a fully recognised route. What it costs is more simulation work at the start and a bulkier certificate at the end. A building simulated properly and drawn to agree with the simulation approves no differently from a prescriptive one — though nobody can guarantee you a plan check result on either route.
You can, and people often do — normally when a window grows, or a wall comes out, and the allowance for glass no longer holds. Timing is what costs money. Change routes after the set is finished and every schedule, section and note has to be reworked to agree with the new run, so it is far cheaper decided early.
It does not. Mandatory measures hold on both routes, with no exceptions. Sealing the building, installing insulation properly, sealing the ducts, lighting, water heating — that is the floor everything else stands on. All performance buys you is room to trade within the package stacked above that floor.
Occasionally. Documentation costs more, but the trade can spare you an expensive envelope upgrade in exchange for something cheaper — a heat pump water heater, a little extra rooftop generation. On a heavily glazed building it tends to be the only route that works anyway, so the honest comparison is not about saving money, it is about keeping the design.
No. They are planning ranges for the energy documentation alone, there to help you budget before the work is scoped. A real figure depends on how large and how complicated the building is, and we would give you one after looking at the project rather than from a dropdown.
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