Design Build

A contracting method where one party is responsible for both designing the mechanical system and installing it. You hold one contract instead of separate agreements with an engineer and a contractor. The practical effect is that design decisions get made with installation cost, lead times and physical constraints already on the table, and that when something does not perform there is nobody to point at but us. The practical cost is that you give up the ability to compare several bids priced against the same drawings.

Four situations, and we will raise them ourselves. When a procurement rule or a board requires competitive bids on identical documents. When you want an independent engineer checking the installer’s work — that referee cannot also be the installer. When the mechanical scope is subordinate to a larger architectural or base-building design that somebody else is coordinating. And when a complete, current engineered set already exists, in which case the sensible move is to price and build that rather than redraw it.

We are a mechanical contractor, and what we do in house is contractor design: load calculations, system concepts, equipment selection, duct and pipe layout, coordination and shop drawings, and sequences of operation. Where a permit, a landlord or an owner requires drawings sealed by a professional engineer, we work with licensed professional engineers who take that design responsibility and seal the documents. We would rather tell you exactly where that line sits at the first meeting than have it surface at filing.

Manual J is the ACCA standard for residential heating and cooling load calculation. It works room by room from construction, insulation, glazing, orientation, infiltration and internal gains rather than from square footage, and it is the correct method for houses and small light-commercial spaces. Larger commercial buildings use Manual N or ASHRAE methods, which add occupancy schedules, ventilation requirements, lighting and equipment loads and diversity between zones. We use whichever standard fits the building. What we will not do is size from the equipment that came out or from an area rule of thumb — that is how a building ends up with too much capacity, poor humidity control and equipment that short-cycles itself to death.

You test it a different way. Ask for the estimate broken into equipment, sheet metal and piping, controls, labour and general conditions so each line can be sanity-checked. Ask for equipment quotes to be shown as received. Agree an open-book approach on changes with a fixed markup set in advance. Some owners bring in an independent cost consultant for a day, which is cheap relative to a mechanical package. And if none of that satisfies the people you answer to, that is a clear sign the project should be bid conventionally.

The calculated load and what equipment type it points to. Ceiling space and structure, which decide whether the distribution is straightforward or a fight. Whether base building capacity — electrical service, gas, chilled water, riser space, roof structure — can carry the new load or has to be extended. Ventilation requirements for the occupancy. Controls scope and how much of it is integration with existing systems. Filing and inspection requirements in your jurisdiction. Working hours, because after-hours work in an occupied building costs differently. We put those on the table with the concept, not at the end.

Often, yes, and we will be direct about what we can stand behind. Work already installed by someone else gets surveyed and reported on before we take responsibility for anything downstream of it. Design work already done gets reviewed against the load calculation. Where an earlier decision is wrong, you get told what it will cost to live with it and what it will cost to correct it, and you decide.

Balancing reports, commissioning records, the written sequences of operation, controls documentation and equipment records are handed over, and the people who will operate the system get shown how. Most of our design-build clients then move onto a planned maintenance agreement with the same company that built it, which means the first service technician on site already knows why the system was designed this way.