Here’s an important question you might not have considered: how do you keep your indoor air fresh in your tiny house? Do you simply keep the bathroom exhaust fan on, or do you have a better way to turn stale air into fresh air? What about pollutants, toxins, and carbon monoxide that might be in your indoor air?
In this article, we explore air exchange systems like heat recovery ventilators and why they are so important for maintaining the freshness, proper humidity, and overall quality of your indoor air.
Is an Air Exchanger Necessary?
With foolproof building technique, tiny house builders can completely seal a home with insulation and other high-performance materials to keep it airtight and prevent energy loss. While that’s great for preventing heat transference, it’s not exactly the kind of environment that would have ready access to good quality air.
We’ve heard the saying that rooms need to “breathe” and that air circulation is important, but what exactly does that mean? Air circulation is crucial, particularly in a small space such as a tiny house, because of the following reasons:
- Pollutants from cleaning supplies, the use of household appliances, or just chemicals seeping out construction materials can linger in the air. Air circulation can help these particles dissipate and introduce fresh, clean air to the home.
- Tiny homes are particularly susceptible to molds. Unlike in bigger homes, bigger spaces mean moisture particles have a wide surface to cover. As in most tiny homes, the shower, the sink, and the kitchen and other moisture-heavy appliances are concentrated in a specific section of the house with not much room to properly dissipate. Not to mention, tiny houses are typically built with wood and other natural materials that could effectively breed mold.
- Offgrid tiny homes running propane appliances are at the risk of carbon monoxide poisoning. Ensuring proper ventilation keeps the air quality clean for the household.
- High humidity levels pose a risk to your respiratory health. Dust, allergens, and other particles can linger in environments with high humidity. Stuffy nose, skin irritation, coughing, and eye irritation are all possible, while also exacerbating asthma symptoms.
Why Exhaust Fans May Not Be Enough
One of the easiest and cheapest ways to let clean air in your tiny home is by simply opening the windows and doors. Fresh air from the outside could come in and replace the stale air from the inside of your home. However, this isn’t always possible during bad weather.
In the winter when condensation and the relative humidity of a home increases, opening doors and windows is not an option.
Most tiny homes are built with exhaust fans and even a range hood to help with the moisture buildup around the kitchen and the bathroom. And while it does improve air circulation in that specific area, it does nothing to change the air quality around your tiny home. Fans built onto range hood and similar appliances simply aren’t built to ventilate entire homes.
Leaving the exhaust fan on in the bathroom and the range hood running will do nothing to regulate the airflow in parts of your tiny house with poor air circulation, including the loft.
To ensure that every nook and cranny of your tiny home is getting fresh air, you need an air exchanger to do the job. Your bathroom fan simply isn’t enough.
How Do Ventilation Systems Work
Ventilation systems, regardless of the type, work to achieve one result: help replace the stale air in your tiny house by bringing in fresh air from outside. While there are different types of air exchange systems used in residential homes, the two most common kinds of systems installed in a tiny house are heat recovery ventilation (HRV or heat recovery ventilator) and energy recovery systems (ERV or energy recovery ventilator).
In both systems, air is drawn in from a vent outside and filtered into your home. Both vent systems use separate airstreams to allow the air inside your home to come out and for the air outside to enter your home. Depending on the unit type, an extra process involving heat transference or dehumidification will be involved in order to make your home more comfortable.
HRV and ERV: What’s the Difference?
HRV and ERV unit systems may overlap but both have a distinct function that distinguishes each from the other. The main purpose of both ERVs and HRVs is to act as the ventilation in a home to vent out stale air and bring in fresh air without need to add heat or coolness to the air.
The most interesting function of heat recovery ventilators and energy recovery ventilators is their ability to filter different kinds of air in a living space, thus allowing them to simultaneously expel stale, accumulated air that is riddled with pollutants, humidity, and toxins and bring in fresh air from the outside.
Additionally, HRVs and ERVs can also help homes during the winter, as they can isolate warm air and transfer the warmth from that air into the incoming outside air. Instead of losing the warmth when the outgoing air leaves the house (and thus needing to generate new heat and spend more energy), this warmth is recycled into the new incoming air.
The ERV goes a bit further than the HRV, with the ability to perform a function known as an “enthalpy transfer”. This means that on top of transferring warmth from outgoing air to incoming air, it can also transfer moisture between these two separate air streams.
This is useful when it is very humid outside and you don’t want that humidity to come in, but you want fresh air. The humidity from the incoming air is transferred to the outgoing air, allowing fresh air to come in without making the interior humid.
Read onto learn more about each kind of ventilation system, and which one to pick for your tiny house.
Heat Recovery Ventilation (HRV)
A heat recovery ventilation (HRV or heat recovery ventilator) system is similar to a balanced vent system but instead uses the existing heat in your house to warm up the incoming fresh air. To make this happen, an HRV typically has two fans: one to bring fresh air and another one to exhaust outgoing stale air.
In a heat recovery ventilation system, heat transference happens in the heat-exchange core. Outgoing and incoming air flows pass through two different airstreams. Although these two different airflows never mix, heat transference is made possible as the heat from the inside of your house is transferred to the cooler air as they pass through the mechanism.
Here’s a clear breakdown of how exactly HRV systems work:
- The air inside of the tiny house is warmed by things inside of the house. This includes everything from your appliances like your boiler, kitchen appliances, and furnace, to natural sources like respiration and body heat
- The warm air of the interior goes into the system. Here, it is moved through a steel or copper heat exchanger
- Via the heat exchanger, the warm air going out passes the heat along to the fresher air coming in, thus adding heat to the exterior air without the need to generate any new heat
- The older stale air is vented out of the tiny house and the fresh incoming air is warmed and circulated. This allows for the distribution of fresh air with no energy or heat loss
HRVs have efficiency ratings that let you know what percentage of the heat of the house is saved. HRVs are typically installed in tiny homes built for colder climates since they are purposefully designed to promote proper air circulation while maintaining comfortable indoor temperatures.
HRVs help conserve heating efforts during the winter by reducing the amount of heat lost as it ventilates your entire house. The best HRVs can have an efficiency rating as high as 85% - which could reduce the total cost of heating your home, alongside using fantastic insulation material during the tiny house build.
While mostly used in colder climates, HRVs also work in reverse. In hotter months, heat from the outside air is transferred to outgoing air, meaning your home won’t need extra cooling capabilities just to achieve comfortable temperatures in the summer. On the other hand, tiny homes located in extremely humid environments would benefit from using an ERV rather than an HRV.
Top Choices For Tiny House HRV
Luckily, choosing a heat recovery vent system for your tiny house isn’t that difficult. Let’s go through some of the crowd favorites in the tiny house community:
1) Zehnder Novus (F) 300 Comfort Ventilation Unit
Zehnder America is one of the most trusted brands out there for HRVs and ERVs, which is why they’re our first shout-out for top HRV choices with the Zehnder Novus (F) 300 Comfort Ventilation Unit. At 93% efficiency, there are few models more efficient than this; your energy needs will be as low as possible with this HRV outfitted in your home.
Known for being very low maintenance, the Zehnder Novus is great at running on its own with little to no manual instruction. This unit has a superior automatic flow control on exhaust and intake air streams, meaning you can essentially just plug and forget.
Broan is another brand that makes both energy and heat recovery ventilators, but our favorite model from their lineup is the Broan HRV250 ECM. While this model might be slightly bigger than what you would be comfortable with (particularly if your tiny house is average or below average in size), this model would work perfectly for above average and large tiny houses that are in need of an HRV that can really handle their home.
This is an incredibly energy-efficient model when it comes to ventilation solutions, with minimal energy consumption at just 18W and 3.6 CFM per Watt at 64 CFM. Those numbers mean this model is perfect for above average tiny houses in very cold areas, as it has a tested 66% heat recovery efficiency at an outdoor temperature of -13 Fahrenheit.
3) LUNOS e2 System
If you’ve done your research on heat recovery systems for tiny homes, then you probably already know about the LUNOS e2, and we agree with the hype: this is definitely the best choice for an HRV in a tiny house. Unlike other HRVs which can be pretty heavy and bulky even in a normal-sized home, the LUNOS e2 seems to be practically built with tiny homes in mind.
The LUNOS e2 is itself a unique system: this compact HRV is actually two separate and individual fan units that work as a pair. The first fan pulls air in while the second fan pushes air out, and the two fans automatically switch every minute or so, alternating between pulling air in and pushing air out. This allows for a clear circulation of air while keep the air fresh.
Another great advantage of the LUNOS e2 is its extremely low power usage, even when used on the highest settings. This is mostly because it is much smaller than other HRVs, built specifically for smaller dwellings. If you need to save as much energy as possible, there is no better HRV to get than the LUNOS e2.
Energy Recovery Ventilation (ERV)
With so much said about HRVs, you might assume that the HRV is your end-all be-all when it comes to air exchange systems for your tiny house. But while an HRV is a fine (and perhaps the optimal) choice most of the time, there are cases where an Energy Recovery Ventilation or ERV system might be better.
ERVs are very similar to HRVs in that they perform all the functionality you can expect from an HRV. The major difference, as stated above, is that ERVs offer the additional function of recovering moisture from the outgoing or incoming air, or the humidity of the fresh air in your home. If the outside is too humid, ERVs will prevent that moisture from coming in; if the inside has more moisture than the air coming in, the ERV ensures that the air becomes humidified before it enters your home’s interior circulation.
Because of this, there are two scenarios where it is better to opt for an ERV over an HRV. These are:
- Humid Climates with Warm Summers: Nobody wants to deal with a hot summer with extremely humid fresh air; nothing feels more uncomfortable than that. An ERV protects you from the outside moisture by trapping the moisture from incoming air and transferring it to the outgoing air. Moist air is actually more difficult to cool down than dry air, meaning than by reducing the moisture in your air, it will cost you less energy to keep your home comfortably cool.
- Dry Climates with Cold Winters: Dry and cold winters mean that moisture is at a premium, with little to no moisture in the air coming in from the outside. The ERV allows you to retain the moisture while refreshing your air by transferring moisture from the outgoing air into the incoming air. Dry and cold air with little moisture can often lead to dry skin and sore throats, so ERVs will protect you from these issues.
Top Choices For Tiny House ERV
Looking for an ERV for your tiny home? Here are some of our top picks:
1) ER80M ERV RecoupAerator
Ultimate Air’s ER80M ERV RecoupAerator is a great choice for tiny houses because it comes in a variety of sizes and it is extremely energy efficient. This model boasts a 45% cooling recovery efficiency and a 99% heat recovery efficiency, which simply means that it’s great at cooling your house in the summer and warming your house in the winter. You also never have to fear winter frost damage, as the unit is built with an internal defrost system.
2) Renew Aire EV 130
Another popular ERV on the market is Renew Aire’s EV 130, which has a typical range of airflow of 50-140 CFM. This unit comes with a low voltage circuit for the control area, meaning it can very easily be used. It might be bigger than what you might need for a tiny house, however, as this unit is also built with commercial buildings in mind.
3) Life Breath 30 ERV
The Life Breath 30 ERV is comparable to the LUNOS e2 System, in that it is generally the ERV of choice for tiny house homeowners due to its compact size and extremely low energy needs. This one is also extremely durable thanks to its aluminum core, with Life Breath itself offering a lifetime warranty on most units they sell.
In a Nutshell (200)
In a nutshell, an air exchanger is an important addition to a tiny house. In such a small and confined space, air can become stale and filled with things you don’t want to breathe; pollutants, toxins, moisture particles, carbon monoxide, and more. This can also be a problem when you are in a region that has high humidity as this can be dangerous for the health and well-being of you and your family, with dust, allergens, and other particles lingering longer in humid air.
HRVs and ERVs are both great options for improving the air in your tiny home, and with just a single purchase you can significantly improve your quality of life by breathing in fresh air without needing to worry about maintaining your preferred room temperature. Here’s what you need to remember when deciding between an HRV or an ERV.
- Tiny homes can benefit from both HRVs and ERVs, so as long as you have one, you’re good
- If you have a smaller than average tiny home and you are mostly in a colder region, you should lean towards getting an HRV
- If you have a larger than average tiny home and you are mostly in a colder region, you should lean towards getting an ERV
- If you are mostly in a humid and hot region, you will save more money with an ERV than an HRV
- If your tiny house will be in both cold and hot regions, you should be fine with either an HRV or an ERV
Secure Your Ideal Air Exchange System Today
Your bathroom exhaust fan and range hood aren’t enough; you and your family deserve only the best when it comes to your tiny house lifestyle, and that includes the air that you breathe. Make sure to choose the best air exchange system for you. Remember, when choosing your HRV or ERV system, look out for the following:
- Whether you need it for a small tiny house or a large tiny house
- The model and brand of the unit
- Your preferred style of system
- Installation costs of your chosen system
- Energy efficiency of the unit
Never deal with too much or too little moisture content, potential carbon monoxide problems, and general humidity again.
Hey, there! We're Ivan and Manuela from Croatia, and we're crazy about tiny houses. We don't own one (yet).
This website is a result of our passion to share all the knowledge, photos, tips and tricks that we were able to learn while studying everything possible about the tiny house movement.