Mechanical Ventilation with Heat Recovery Explained (MVHR)

11 Jun

Due to techhnological and insulation advances, our homes are becoming more air-tight and better insulated than ever. This is a great thing for us in the UK, where we live in old victorian-era homes that leak air like there’s no tomorrow, meaning you’re losing that valuable heat needed to keep you warm.

With modern homes and building regulations, new builds are required to install more insulation to help keep our homes better insulated. But when it comes to better insulated homes and more air-tight ones, the need to allow ventilation into the home is even more important.

Take the home you may be living in now, it has various places for heat and air to escape - be it intentionally or not. But a modern, air-tight home, means you need to remove the stale air and allow for fresh air to be piped in, to ensure a healthy home for you and your family.

What is Heat Recovery Ventilation (HRV)?

Heat Recovery Ventilation (HRV) is a system that uses the heat in stale air within piping or ducting to preheat incoming fresh air from the outside. This can significantly reduce the energy required to bring outside air up to room temperature, saving you money on energy bills.

Energy Recovery Ventilation (ERV) is essentially the same as a HRV but it removes some of the moisture/humidity in the air. Whilst this may not seem immediately important, excess moisture in the air from cooking, showering or even breahting, can result in mold formation.

For a tiny home, be it 15m2 or 40m2, it’s likely going to be insulated well, with a tight-build, meaning that air can be trapped easily and moisture will have less chance of escaping like a normal-sized home, and that’s why we recommend all Tiny homes to have a system that can reduce your energy bills whilst removing the moisture in the air.

What are the benefits of a MVHR system?

Well, if you live in a Tiny home or even a large normal-sized home, all homes need a form of air-flow. In most British homes, the walls have a small opening to allow air in and out of the home. As you can imagine, that can bring down the temperature of a home significantly in the winter, and even bring in pollutants from the air. Another way to remove stale air from the home and bring in fresh air, is simply to open a window however with the infamous British weather, you know at times opening windows could be a bad idea, if there’s sleet or heavy rain, or it’s simply freezing outside.

With a HRV/MVHR system, the air that would normally be moved around by opening a window or the opening in the wall, can now be done via the machine. With the movement of air, comes heat, and sometimes heat is something that we want to remove from the home. In comes the HRV/MVHR system.

Heat can be extracted from stale air, through the air-to-air heat exchanger within the HRV/MVHR system, which is consequently used to warm the incoming fresh, filtered air to the room or house. Some studies have shown that up to 96% of the heat generated within your home can be kept - significantly reducing the need for external heating.

The HRV/MVHR system is highly-prized within the passive-house community, allowing people to simply heat their homes at a comfortable temperature with just their own body heat and day-to-day activities, from cooking to showering. It can also remove high levels of moisture, meaning that if you’re worried about mold forming or you’re sensitive to airborne particles such as pollen, the filter can remove these from the air, helping you breath cleaner air.

When living in a small home, such as a tiny, the benefits are even more pronounced. With a few people within the home, cooking, eating, breathing, all within a smaller space, moisture can build up in the air more easily, and that’s where the HRV/MVHR can help reduce this in the air, whilst ensuring your home is at a comfortable temperature. If the tiny home has a lot of insulation and is very air-tight, then there’s even less chance of this moist air to escape, so the HRV/MVHR system is even more important.

HRV Vs ERV - What’s the difference?

The choice between an HRV and an ERV depends on your climate and specific needs. If your house is too humid in winter (above 60% relative humidity) then an HRV is the better choice, as it would surely get rid of excess humidity while an ERV would tend to keep it at a high level.

With us living in the U.K, winters are typically dry and cold - with little humidity. So an HRV system is more suitable to our climate.

But if you’re not in the U.K, you’ll need to look into your local climate area - if you live somewhere with a lot of humidity, and it’s warm, then an ERV may be best for you.

With Tiny homes, we’ve heard the stories of other homes that don’t provide an ERV or HRV, that the homes can at times have the humidity build up so much from the occupants’ own natural breathing that evaporates and results in condensation. With tiny homes being compact, and lofts being low in terms of height, it’s easy to see why a suitable ventilation system is required to ensure the heat is not only moved around the home, but the humidity is also taken out - ensuring you don’t have a mold problem in the future.

Summary

We aim to build our homes as air-tight as possible at The Tiny Housing Co. This means we use materials such as SIP frames that are highly insulative to ensure your home does not leak air or heating. It also means that heating your home is easier as a small well-insulated space requires very little heating. Putting on a wood burner for an hour or a heater for an hour or two can radiate heat in home for the full day. If you add a wall-mounted HRV or a MVHR you’ll not only get clean, safe air for you and your family but also a better-ventilated home.

Our chosen HRV system has a HEPA filter which filters out 99% of pollution and other toxicants in the air. Even if you park your Tiny in the countryside, you’ll experience air pollution, so with the ability to reduce that and remove humidity from your home, we believe an HRV is simply a no-brainer.

For more information about our homes, and what we have available, click here to view our range.