Don’t renovate without improving airtightness and ventilation
Cosmetic upgrades alone won’t fix cold, uncomfortable homes.
A modest investment in airtightness and ventilation transforms comfort, health, and energy performance.
Mould and mildew are common, contributing to some of the worst respiratory health stats in the OECD. Traditional upgrades like removing wall linings to install insulation are costly and highly disruptive. The EnergytightTM Retrofit Solution makes it easy to significantly improve energy efficiency and comfort in existing homes.
Note: Every home is different, and while Energytight™ aims to deliver excellent results in both new builds and retrofits, outcomes depend on many factors—read our full disclaimer here to learn more.
Improving airtightness and ventilation is a low-cost, low-disruption way to
significantly improve a home’s comfort, health, and energy efficiency.
Instead of removing wall linings to install insulation, the Energytight™ approach
focuses on sealing air leaks and adding heat-recovery ventilation, delivering
greater overall performance at a fraction of the cost and disruption.
Based on IECC data, traditional insulation and window upgrades can reduce
energy use by around 60%, while airtightness, ventilation, and window
improvements can achieve reductions of around 67% — with walls left intact.
If you are renovating, airtightness and ventilation are an essential part of the
project. Without them, major renovations can still result in cold, damp homes,
while a modest additional cost delivers a clear step-change in comfort, health,
energy efficiency, and durability.
Traditional Renovation
(Add wall insulation. Don’t address airtightness)
Potential Energy Use Reduction 61%
Energytight™ Retrofit
Potential Energy Use Reduction 67%
Deep Renovation
(Traditional renovation plus Airtightness)
Potential Energy Use Reduction 100%
Source: Based on IECC data from NEHERS presentation, ANSI/RESNET Conference, November 2023 and ENERGY STAR publications.
The One Tree Hill College Trade Academy renovated a 1970s ex-Kāinga Ora state house to showcase how standard New Zealand homes can be upgraded to high-performance levels using conventional methods, plus airtightness. The project aimed to exceed building code standards and successfully achieved Homestar 7 certification.
This case highlights how energy-efficient, healthy, and durable homes can be delivered affordable when airtightness and ventilation are prioritised.
Summary
Starting airtightness: 19 ACH50
Final airtightness: 1.7 ACH50
Achieved Homestar 7
Key goal: Prove that ambitious airtightness targets (below 3.0 ACH50) can be achieved in typical homes
“We’ve taken a 1970s Kāinga Ora home from 19 air changes down to just 1.7 ACH50—a level of performance well beyond most new builds. Absolutely amazing.”
If you’re renovating, don’t invest in a major upgrade only to end up with a cold, damp, uncomfortable home. The best time to add airtightness and ventilation is while the house is empty.
With no furniture and work already underway, the Energytight™ Solution integrates easily with your builder and architect, delivering major gains in comfort, indoor air quality, energy efficiency, and building durability for a minor additional cost.
If you’re not renovating, an Energytight™ retrofit is a low-disruption way to improve comfort, health, and efficiency. While it’s ideal when the house is clear of furniture, it can also be carried out in occupied homes with some additional preparation.
| Process | Deep Renovation | Traditional Renovation | Energytight™ Retrofit |
|---|---|---|---|
| Add ceiling and floor insulation |  | | |
| Remove wall linings | | | |
| Remove skirting and architrave | | | |
| Create wall cavity | | | |
| Install wall insulation | | | |
| Fix and stop new wall linings | | | |
| Fix skirting and architrave | | | |
| Remove windows | | | |
| Fit new frames and windows | | | |
| Retrofit new glazing in existing frames | | | |
| Airseal house | | | |
| Install ventilation system | | | |
| Potential impact on energy saving - based on IECC data. | 100% | 61% | 67% |
Source: Comparison based on IECC data from NEHERS presentation, ANSI/RESNET Conference, November 2023
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