Blog - Sustainable Engineering Ltd.

How long do our houses actually last? The 90-year reality

Retrofitting for performance only makes sense financially, at least when you’re already renewing a building element. Ripping off perfectly good cladding to add insulation is a tough sell, but doing...

Updated: Feb 2026

Ventilate right: ignoring this endangers health

Is Passive House still relevant now that heat pumps are efficient and the grid is decarbonising? Nick Grant tackles this in a recent post, and while the energy arguments are...

Updated: Feb 2026

EnerPHit vs the ‘lite’ alternatives

I’ve been deep in the weeds working on the Deep Energy Retrofit Guide for New Zealand, and naturally, that means looking overseas for data we simply don’t have here yet....

Updated: Feb 2026

Short stays in Passive House homes in Aotearoa New Zealand

I’ve been describing the features and benefits of Passive House buildings for years but even my best words can’t convey as much as directly experiencing it with all your senses....

Updated: Jan 2026

What is “drier”? Relative versus absolute humidity in Auckland

I’ve just finished reading a new paper in the Journal of the Royal Society of New Zealand by Rochelle Ade, Mike Rehm, and Vishnupriya: “What is drier? Understanding humidity in...

Updated: Jan 2026

Burning stuff indoors is a $12 billion health bill

In our Passive House design and certification work, we often push clients to ditch gas hobs and wood stoves. Usually, we talk about airtightness, energy efficiency, and the fact that...

Updated: Jan 2026

Building science déjà vu: why we keep rotting our homes

In old homes we had (and have still in those not retrofitted) lots of energy flowing through the building elements: walls roofs and floors. This was due to lack of...

Updated: Jan 2026

A masterclass in detail: visiting a Japanese Certified Passive House

One of the best perks of working in this community is the people you meet. I first bumped into Miwa Mori at our very first PHINZ conference back in 2015....

Updated: Jan 2026

98% failure rate: The UK’s retrofit warning

A new report from the UK’s National Audit Office (NAO) dropped recently, and the numbers are frankly terrifying. “Under the Energy Company Obligation (ECO) scheme, 98% of homes retrofitted with external...

Updated: Jan 2026

Sharing the Sun: Why high performance is essential for a fair grid

I was super thrilled when Philippa Howden-Chapman invited me to contribute to a new book, Sharing the Sun: Empowering small-scale renewable generation in Aotearoa. Edited by Helen Viggers, Keriata Stuart, and...

Updated: Jan 2026

Streamlining certification for multi-building projects

If you are working on a project with multiple thermal envelopes—even if they are just separated by breezeways—you need to remember the ground rules. Separate thermal envelopes imply separate PHPPs,...

Updated: Jan 2026

High performance airtightness costs no extra carbon

I wanted to point out a recent LinkedIn post by Sally Godber from WARM in the UK. I know Sally from discussions at a few Passive House conferences; she is a straight...

Updated: Jan 2026

EVs add to winter energy demand peaks

New research is a sharp reminder that if New Zealand wants a stable, affordable, 100% renewable grid, reducing demand is just as critical as increasing supply. The choices we make—about...

Updated: Jan 2026

How much is healthy indoor air worth? This study has an answer

The energy savings offered by building to the Passive House standard are easy to quantify. The comfort and healthiness of these homes is very much felt by those living in...

Updated: Feb 2026

PHINZ hui 2025: a summary and ideas for next year

What did you enjoy most? Well, talking to mates about Passive House is always my favourite. The Pecha kucha thing though! My expectations were low, I’m not familiar with the...

Updated: Jan 2026

Energy performance certificates for NZ homes

Talk of mandatory energy performance certificates (EPC) for New Zealand homes is always guaranteed to spark a lively debate. I admit to still being a bit on the fence on...

Updated: Jan 2026

Ara collab spreads Passive House influence

Ara Institute of Canterbury, a leading provider of construction training in the region, was the location for Sustainable Engineering’s last in-person certified Passive House tradesperson course. It was a great...

Updated: Jan 2026

How to talk to your clients about Passive House

Model’s plans for massive build-to-rent Passive House developments in Melbourne was what set the 2025 Thrive conference in Australia buzzing but there were other presentations that really galvanised my attention. Kieran Leong...

Updated: Jan 2026