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.

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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:

1. 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
2. The warm air of the interior goes into the system. Here, it is moved through a steel or copper heat exchanger
3. 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
4. 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) Fantech Flex 100H Heat Recovery Ventilator

This HRV is typically used in three to four-bedroom homes but is more than enough in keeping your tiny home’s air safe and breathable. Its aluminum core provides unrivaled heat transfer capabilities. Fantech’s exclusive TurboTouch feature allows the device to deliver 50% more exhaust capabilities whenever extra airflow is needed.

It’s a great feature to have if you live in particularly arid and stifling environments. This HRV system’s compact size makes it the perfect option for even the smallest of tiny homes.

2) Broan HRV250 ECM

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) Honeywell VNT5200H1000 HRV

Honeywell’s upfront costs may be pricier compared to other HRVs on the market, but the ease of installation might be what makes you consider this over the other choices. With this Honeywell HRV, you don’t need to worry about overhead ducting and making time-consuming installations. It’s a great option for DIYers who want a straightforward and reliable system installed in their tiny home.

It features centralized wiring and speed control for ease of use, allowing up to 200 CFM of airflow. The device is also powered with defrost control, making it a viable option even in cool weather. With two operating modes, homeowners can choose depending on their needs and energy capabilities.

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) Fantech SE704N Energy Recovery Ventilator

This Fantech model sports the traditional design with two side ports. This ERV is equipped with defrost capabilities, giving homeowners in colder climates a fail proof option. This particular model is powered by an enthalpy core and an electronic control board for easy access. It uses an aluminum heat recovery core for improved heat transfer capacity despite its compact size. With washable electrostatic filters, you can keep your home’s air clean and comfortable. 

2) Panasonic FV-10VE1 Intelli-Balance 100 Energy Recovery Ventilator

Don’t let its size fool you: the Intelli-Balance 100 ERV is perfect even for larger tiny homes. This ERV is equipped with a customizable airflow controller so homeowners can dictate the air pressure in their tiny homes.It’s specifically made for North American Climate Zones so it’s ready for both incredibly harsh winters or sultry summers. An automatic defrost cycle kicks in after reaching below 14 degrees Fahrenheit, allowing the device to self-start and work optimally in winter. 

3) Broan ERVS100S

This ERV from Broan takes pride in recovering up to 71% of excess heating and cooling. Powered by the Broan’s proprietary Venmar Core Technology, this powerful ERV can decrease indoor relative humidity by up to 51%, keeping your air quality as comfortable as possible. Built-in sensors for humidity and temperature inform the device every 10 minutes, allowing it to adjust its performance even without any set-up required. 

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.