The methodology

Sort the building out first. Add plant last.

Most design teams already work in this order. Cut the heat and the pollutants the building has to deal with, get the fabric right, ventilate it without fans, and only then add mechanical systems for whatever is left. Passive-First is just the name we give that sequence. We have written it down because the ventilation step is the one that usually breaks, and it is the step we know most about.

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The hierarchy

Five decisions, in order

The order matters. Each step changes the size of the problem the next one has to solve.

1

Cut the heat gain

Orientation, glazing, shading and thermal mass. Heat you keep out of the building is heat you never have to shift back out of it.

2

Build it tight and insulate it well

The fabric decides how much heat the building loses and how much it holds on to.

3

Ventilate without fans, and keep the heat

Wind and buoyancy move the air through the building. A heat exchanger keeps the warmth in. This is the step that usually gets skipped.

4

Keep mechanical ventilation for the spaces that genuinely need it

On the projects we see that is usually the kitchen and the WCs, which stay on extract. Send us the room schedule and we will tell you which rooms Windhive can ventilate.

5

Serve what is left with the smallest plant you can

Less kit to buy, less to run, less to maintain for the life of the building.

Step three is where it tends to fall apart. A team gets the gains down, gets the fabric right, and then specifies a mechanical system anyway, because going passive looks like giving up heat recovery. Windhive exists because you do not have to make that choice.

The questions

Four questions we get asked, and how we answer them

These come up in CPD sessions, in design team meetings and at tender. They are fair questions, and these are the answers.

What we get asked

Passive ventilation cannot recover heat. If you want heat recovery you need fans.

What we can show you

This is the assumption Windhive was built to test. A heat exchanger sits inside the unit and transfers warmth from the air leaving the room to the air coming in. Wind and buoyancy do the moving, so there is no fan and the only moving parts are the dampers.

What we get asked

Is it weather dependent? On a still day, or a cold one, would it stop working?

What we can show you

No, Windhive will still ventilate in those conditions because buoyancy takes over when the wind drops, and buoyancy is strongest when the temperature difference between inside and outside is largest.

What we get asked

My contractor has never fitted one, how do you support the contractor?

What we can show you

We are committed to the highest level of service and support, and our customers are at the heart of everything we do. That is why we train the installer and commission the units ourselves. We will talk to your preferred contractor directly at tender stage to help and support them through the process.

What we get asked

An opening window does much the same thing for a fraction of the cost.

What we can show you

Opening a window loses the heat. With Windhive you are still naturally ventilating the space but also recovering the heat, which means saving money and energy on the heating bill.

Facing that trade-off on a live project?

Bring us in at concept stage and we will give you four things for your building: a thermal model, the compliance position, unit sizing and layout, and a budget cost. If Windhive is the wrong answer for the project, we will tell you.

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Elsewhere on the site

Where to go next

Windhive

The product, the performance data and the basis of every claim we publish.


Sectors

How this works in schools, sports halls and community buildings.