Modern houses are built to be super energy-efficient, which is great for keeping heating bills low in winter. However, on warm summer days (when we are lucky enough to have them) our homes can become uncomfortably warm. This can be emphasised when there is a lot of glazing in the home as this increases solar gain, causing overheating within the home.
So you may wonder an MVHR system which is essentially designed to recover heat from outgoing stale air would make things worse. But this is not the case. MVHR systems are designed to provide comfortable indoor environment year long.
How MVHR Adapts in Different Climatic Conditions?
While their core function of providing fresh, filtered air remains constant, the way they achieve this differs between summer and winter.
During the colder months, MVHR acts as a heat exchanger. As it extracts stale, warm air from your home (think kitchens, bathrooms, and utility rooms), it cleverly captures the heat energy trapped within. This extracted heat is then transferred to the incoming fresh air coming from outside. The result? Pre-heated fresh air gently circulated throughout your home, providing a comfortable warmth without relying solely on your central heating system. This translates to significant energy savings and a cozy winter haven.
Here’s where things get interesting for summer. Many MVHR systems come equipped with a clever feature called a “summer bypass.” The system keeps an eye on the outdoor temperature. When the outdoor temperature dips lower than the indoor temperature (often during nights or early mornings), the summer bypass kicks in.
Instead of using the heat exchanger, the bypass redirects the hot indoor air directly outside, preventing it from re-entering your home. The system then draws in the cooler outdoor air. Even with the bypass engaged, the MVHR still utilizes the heat exchanger to a minimal extent. This ensures the incoming cool air isn’t excessively chilly, creating a gentle and pleasant cooling effect.
The pre-heated (but still cool) fresh air is then circulated throughout your home, naturally lowering the overall temperature and keeping you comfortable.
How does MVHR Summer Bypass Work?
The key component responsible for summer bypass functionality is a strategically placed damper within the MVHR unit. This damper essentially acts as a controllable gate, regulating airflow through the heat exchanger.
Here’s how the bypass operates:
- Monitoring Magic: The MVHR system continuously monitors both indoor and outdoor temperatures.
- Triggering the Bypass: When the outdoor temperature falls below a pre-set threshold (often lower than the desired indoor temperature), the control system recognizes an opportunity for natural cooling.
- Damper in Action: The control system activates the damper, causing it to shift and divert the warm, stale air extracted from your home directly outside.
- Bypassing the Heat Exchanger: With the damper positioned for bypass, the hot indoor air no longer passes through the heat exchanger. This prevents the heat from being transferred to the incoming fresh air.
- Drawing in Cooler Air: Simultaneously, the system opens another pathway, allowing cooler outdoor air to enter the unit.
MVHR vs. Air Conditioning: Finding the Right Fit
MVHR isn’t an air conditioning system. It doesn’t blast cold air to instantly chill your home. Instead, MVHR takes a strategic approach, tackling the root cause of overheating – excessive solar gain through windows – and focusing on ventilation and air quality to create a naturally cooler and healthier environment.
Unlike air conditioning, which relies on refrigeration to cool the air, MVHR systems operate by exchanging heat between the indoor and outdoor air streams. This not only helps to regulate indoor temperatures but also reduces the need for mechanical cooling, resulting in lower energy consumption and utility costs. Additionally, MVHR systems provide continuous ventilation, ensuring a constant supply of fresh air throughout the home, whereas air conditioning units may recirculate stale air.
Here’s a quick breakdown:
| Feature | MVHR | Air Conditioning |
| Primary Function | Ventilation & Heat Recovery | Cooling |
| Summer Cooling | Yes (through summer bypass) | Yes (directly cools air) |
| Energy Efficiency | High (heat recovery) | Varies |
| Cost | Moderate | Varies (installation & running) |
| Installation | Less complex | More complex |
MVHR systems are a fantastic choice for homeowners who prioritize consistent ventilation, improved air quality, and energy efficiency. While they might not provide the intense cooling power of an air conditioner on a scorching day, they do offer a more natural and sustainable approach to summer comfort, especially in the Irish climate where extreme heat is less frequent.
Here are some additional benefits of MVHR over air conditioning:
- Reduced humidity: MVHR systems can help control humidity levels, making you feel cooler even at slightly higher temperatures. This is because moist air feels hotter than dry air.
- Improved air quality: As mentioned earlier, MVHR constantly filters and replaces air, removing allergens and pollutants that can exacerbate allergies and asthma.
- Year-round comfort: The same MVHR system that helps you stay cool in summer also keeps you warm and comfortable in winter by pre-heating fresh air with outgoing stale air.
Will opening my windows effect the efficiency of my MVHR system?
You can open windows with heat recovery ventilation systems
In the summertime, when we experience hotter weather, you can open your windows. Your ventilation system will continue to work as you are not depending on the heat recovery element.
The only downside would be to serious asthma or allergy sufferers as the air coming in through the open windows would not be filtered, but it is still fresh air!
Bonus Tips for a Cool and Comfortable Summer
While MVHR is a powerful tool for keeping your home cool and comfortable during summer, there are some additional strategies you can employ to further enhance the effect and create a refreshing haven:
- Embrace Natural Ventilation: Take advantage of cooler night-time air! Open windows strategically in the evening and allow for natural cross-flow ventilation throughout your home. Remember to close the windows again once the outdoor temperature starts to rise during the day.
- Blinds and Curtains: Keep south-facing windows shaded during the hottest part of the day. Blinds, curtains, or awnings can significantly reduce solar gain and prevent your home from turning into a greenhouse. Opt for light-colored window coverings to reflect heat further.
- Lighting Choices: Incandescent bulbs generate heat. Switching to LED lighting options can help reduce heat generation within your home.
- Hydration is Key: Staying hydrated is crucial during summer. Drinking plenty of water helps regulate your body temperature and keeps you feeling cool from the inside out.
- Low-Tech Cooling Solutions: Simple tricks like taking cool showers, wearing loose, breathable clothing, and using fans strategically can all contribute to a cooler feeling environment.
Get in Touch
Remember, MVHR isn’t just for winter! It’s a year-round solution for maintaining a healthy and comfortable home environment.
At Flynn Heat Recovery Systems, we understand that everyone’s needs are different. We offer a wide range of MVHR systems to suit all budgets and home sizes. Our friendly and knowledgeable team can help you choose the perfect system to keep your home cool, comfortable, and healthy year-round.
Contact us today for a free consultation!