Parenga House

Projects
Parenga House

Parenga House

Location	Hautere, Otaki, Kapiti Coast
Client	Owners: Hugh Tennent (Owner / Architect) Architect: Tennent Brown Architects Engineer: Focus Engineering Builder: Duncan Construction
Prolam Products	Prolam PL12 H3.2 Beams Prolam PL8 H3.2 Beams Prolam PL8 H3.2 Posts

An architect’s own home, Parenga House has been designed on passive house principles, low embodied carbon and a commitment to timber – structurally, materially and aesthetically.

Designed by Hugh Tennent of Tennent Brown Architects for himself and his wife, the home sites on a riverside site near Hautere, surrounded by mature native trees. It replaces the couple’s former summer batch with a four-season home designed to work with the site, climate and landscape.

Hugh’s commitment to passive house principles is written in the architecture of Parenga House – with an all-timber structural approach that defines its roofline, interiors and outdoor spaces.

Designed around timber

Passive house principles shaped the design from the outset, with Hugh focused on strong thermal performance and low embodied carbon.

Strong thermal performance and low embodied carbon were central to the design from the outset.

The house incorporates exterior insulation, heat recovery ventilation and a high-performance thermal envelope as part of Hugh’s aim to create a home that would be comfortable in every season. A full life-cycle assessment put the home’s embodied carbon at approximately 340 kgCO₂e/m², which Hugh notes is close to the RIBA residential 2030 target of 300 kgCO₂e/m².

The structural material choices were part of that low-carbon strategy, with Prolam glulam, CLT panels and conventional timber framing used throughout the home.

Timber was also central to the architectural expression. Prolam visual grade glulam forms the long rafters running across the ceiling and extending out over the veranda, along with the structural barge board and paired posts supporting the porch and conservatory roof.

As Hugh explains: “It’s all wood, the whole thing. I really wanted to explore a fully timber house, and Prolam let me do that outside as well as in.”

Engineering the cantilever

One of the defining features of Parenga House is the long line of Prolam rafters extending from the interior out over the veranda.

Twenty-two 240 x 63mm Prolam PL12 H3.2 Beams, each 7.8 metres long, form the rafters and create an approximately 2.7-metre cantilever over the outdoor living area. A 450 x 42mm Prolam PL8 Beam forms the structural barge board, while paired 190 x 63mm Prolam PL8 Posts support the veranda, porch and conservatory roof.

The combination of cantilever and back-span requirements sat outside the standard information available through the Prolam Specifier, so David Lai of Focus Engineering developed a Specific Engineering Design using span tables and data provided by the team.

The finished rafters deliver the structural performance required while creating one of the home’s most distinctive architectural features – with their length and repetition carrying the timber structure from the interior out over the sheltered outdoor living space.

Visual performance outdoors

Where the structure is exposed to the exterior, both durability and appearance were important parts of the specification.

All of the Prolam glulam members were manufactured supplied in visual grade and H3.2 MCA treated, then finished with a light-coloured Resene wood stain. The treatment and coating combine to provide the long-term protection required for exposed exterior use, allowing the rafters, barge board and paired posts to remain visible rather than being boxed in or clad.

The choice of MCA treatment was also important to Hugh. Avoiding Red List materials was part of the project’s wider material approach, and MCA-treated Prolam aligned with that objective.

“That's one of my attractions to Prolam products. It makes it an easy choice to specify – for exterior performance, non-toxic treatments, everything."

Built with confidence

For builder Nathan Fredstig and the Duncan Construction team, the scale of the Prolam members was the main consideration on site. At 7.8 metres long, the rafters required some manoeuvring into position, but Nathan found them stable, straight and straightforward to work with.

The finished cantilever was a particular success.

“It was a significant cantilever over a large outdoor area, and it came together really well. The beams stayed straight, with no sagging. It looks stunning.”

A considered material approach

Prolam sits within a carefully considered material palette across Parenga House.

Alongside the locally made glulam engineered from New Zealand plantation-grown Radiata Pine, the home uses Lawson cypress, birch ply and recycled matai internally, high-performance timber windows and recycled-content rigid air barrier board.

Together, those choices reinforce the same principles that shaped the structural design — low embodied carbon, considered material selection and timber expressed as an integral part of the architecture.

"Prolam’s combination of performance, durability and architectural quality is very valuable in the work we do. The known properties, consistency and MCA treatment make it particularly well suited to exposed applications, while also aligning with the kind of low-carbon, considered material choices we are trying to make.”
— Hugh Tennent, Tennent Brown Architects