Donald Drive

Luxury Finishes. Building Science Precision. Built to Last a Lifetime.

When the client for this Orinda project came to us, he wasn’t a typical homeowner. Richard grew up in this house. He is also a licensed architect, a former City of Oakland building inspector, and an expert witness in construction defect litigation. He knows what good work looks like — and what bad work looks like. He hired Scott O’Hara Construction.

The scope was substantial: a 600-square-foot room addition, a new 1,096-square-foot fire-rated IPE deck with custom metal and wood railing, and high-end interior upgrades throughout. The mechanical systems were fully replaced and engineered from the ground up using Building Science principles. And because this home sits in a Wildland-Urban Interface zone, every decision — from the roof to the crawlspace — was made with fire hardening in mind.

The Craft

The owner grew up in this house and had a specific requirement: preserve the exterior character of the home while transforming everything inside and out. We did both.

Fire-Rated IPE Deck — 1,096 Square Feet
The existing deck was replaced with 1,096 square feet of Ipe — one of the most durable and fire-resistant hardwoods available. The custom metal and wood railing was designed and fabricated to complement the home’s existing aesthetic. Every connection detail was completed to fire-hardening standards: no hidden wood edges, no places for embers to accumulate.

Custom Redwood Siding Over Fire-Rated Sheathing
Maintaining the exterior look the client loved meant using custom redwood siding — but doing it the right way. The siding was installed over 5⁄₈” Dense Glass sheathing, which provides a non-combustible substrate and significantly improves the home’s resistance to radiant heat and ember intrusion at the wall assembly level.

600 Square Foot Room Addition
The addition was integrated into the existing structure to match the home’s character seamlessly — same roofline, same exterior materials, same attention to detail. From the street, it looks like it was always there. Inside, it added meaningful, fully-finished square footage with the same quality of finish work as the rest of the home.

Interior Upgrades Throughout
High-end finishes and upgrades were carried throughout the home — consistent with the level of detail you see in the exterior and systems work. Every room reflects the same standard: no shortcuts, no value-engineering out the things that matter.

The Building Science

This is where most contractors stop paying attention. We don’t. Every mechanical and envelope decision on this project was guided by Building Science — the applied discipline of understanding how air, heat, and moisture move through a home. The result is not just lower energy bills. It is a home that is genuinely more comfortable and healthier to live in, and significantly more resilient to wildfire.

Right-Sized HVAC: 3 Tons Instead of 6
The industry standard approach to HVAC sizing is roughly 1 ton of capacity per 500 square feet — no engineering, no analysis, just a rule of thumb that reliably results in oversized equipment. An oversized system short-cycles: it heats or cools the air quickly, shuts off before it can dehumidify properly, and creates hot and cold spots throughout the house.

We do it differently. We performed a Manual J load calculation and a Manual D duct design using WrightSoft software before specifying a single piece of equipment. The result: two Fujitsu ducted mini-split heat pump systems totaling 3 tons — half what a rule-of-thumb contractor would have installed. The ductwork was tested and confirmed to have zero leakage.
What Richard didn’t tell us until after they moved in was that he had quietly doubted it the whole time. As an architect and former building inspector, he had privately questioned whether the smaller duct runs — a natural result of right-sizing to 3 tons rather than 6 — would distribute air properly throughout the house. He never said a word about it during the project.
The system runs longer cycles at lower output, dehumidifying properly and delivering even, consistent temperatures throughout every room. After they moved in, Richard told us he hadn’t been sure it would work — and that they were very impressed with how comfortable the house is. That quiet admission, from a man who has spent his career identifying construction failures, is the best review we could ask for.

ERV: Engineered Ventilation
A new Energy Recovery Ventilator (ERV) was engineered with Manual J and D calculations and installed without duct leakage. The ERV continuously exchanges stale indoor air with filtered fresh outdoor air — recovering the energy from the exhaust air in the process. The result is controlled ventilation that improves indoor air quality without wasting heating or cooling energy.

A Note on Air Sealing
This project involved a room addition and targeted renovation — not a full gut of the entire existing structure. Because a portion of the home was not opened up, we did not pursue extremely low blower door numbers, and we won’t represent otherwise. What we did do: tape the exterior plywood sheathing as an air barrier, seal the attic assembly, and seal the crawlspace. The result is a home that is dramatically tighter and better-performing than it was, and one that tests as clean and comfortable in practice — which is what mattered most to the owners.

“He never said a word about his doubts during the project. After they moved in he told me he hadn’t been sure the smaller duct runs would heat and cool the house properly. They were very impressed with how comfortable it is. That’s Building Science working exactly as it should.”
— Scott O’Hara, Scott O’Hara Construction

Sealed & Conditioned Crawlspace
The crawlspace was sealed with a 15-mil vapor barrier and a rat slab was poured throughout. All existing crawlspace vents were removed and the space was fully conditioned — a detail that delivers on three fronts simultaneously: better indoor air quality (no ground moisture and mold pathways), improved energy efficiency, and significant fire hardening (no open vents for embers to enter the subfloor cavity). Great at keeping rats out as well.

Attic Assembly: Rigid Foam Above the Roof Deck
The attic was sealed and rebuilt with 2 inches of rigid foam installed above the roof deck. This moves the condensation plane above the waterproofing membrane — the correct Building Science approach for this climate — and creates a continuous thermal and air barrier at the roof level. This detail improves comfort, reduces energy load, and eliminates one of the primary pathways for ember intrusion in a wildfire event.

Wildfire Resilience

This home is in a Wildland-Urban Interface zone in the East Bay hills. Wildfire resilience was not an afterthought — it was a design criterion for every system and every assembly on this project.

Off-Grid Fire Suppression System
Code required interior fire sprinklers. We went further. During the project, we ran a dedicated pipe from the bottom of the pool to a fire suppression pump that is plumbed into two separate systems: the interior sprinklers and a separate yard-watering system designed to wet the perimeter of the property during a wildfire.

The critical detail: this system runs off the home’s battery storage system or the backup generator. When PG&E goes down and municipal water pressure fails — the exact scenario that occurs during the East Bay wildfires most likely to threaten this home — the fire suppression system still works. This system was presented at the 2026 Forum on Measured Home Performance alongside researchers from Lawrence Berkeley National Laboratory.

Standing Seam Metal Roof with Ember-Resistant Details
A standing seam metal roof was installed with carefully executed details to ensure all exposed wood edges at eaves, rakes, and penetrations are covered with metal. Gutter guards were installed to prevent debris accumulation in gutters — a common ignition point when embers land in dry leaf litter.

Fire Sprinklers: Interior & Eaves
Sprinklers were installed both in the interior of the home and in the eave overhangs — a code-required and fully engineered system that is backed by the pool-fed suppression pump and independent power source described above.

Non-Combustible Exterior Assembly
Custom redwood siding over 5⁄₈” Dense Glass sheathing. Sealed crawlspace with all vents removed. Sealed attic with rigid foam above the roof deck. Each of these details, taken individually, reduces fire risk. Together, they create an exterior assembly that is meaningfully more resistant to ignition from radiant heat and ember accumulation than a standard construction approach.

Energy & Grid Resilience
The home was equipped with a full solar and battery storage system along with a backup generator — all integrated with the home’s all-electric mechanical systems. This is not just about lower utility bills. In an era of planned safety shutoffs and wildfire-driven grid failures in the East Bay hills, the ability to operate off-grid is a fundamental quality-of-life and safety feature.

Project Highlights

The client for this project could have hired anyone. He is an architect. He has spent his career inspecting construction and testifying in defect cases. He chose Scott O’Hara Construction.

If you are planning a renovation, addition, or new construction in the Lamorinda or Diablo Valley area and you want a contractor who will engineer the systems properly, build the finishes to match, and stand behind the work — we would welcome a conversation.