Free tools Windows power users keep installed
One-click scans. No signup required.
Some links on this page are affiliate links: if you buy through them we may earn a commission, at no extra cost to you.
Heat-recovery ventilation in a Passive House continuously replaces stale indoor air with filtered outdoor air while transferring much of the outgoing air’s heat to the incoming air. It reduces the heat lost through ventilation; it does not generate heat or replace a heating system. The result depends not just on the exchanger’s efficiency, but also on balanced airflow, fan electricity, frost protection, ductwork and commissioning.
What does heat-recovery ventilation do in a Passive House?
A Passive House is built to be highly airtight. That limits uncontrolled drafts and heat loss, but it also means leakage through the building envelope cannot be relied on to remove moisture, odors, carbon dioxide and other indoor pollutants. A mechanical ventilation system provides a planned, continuous route for fresh air in and stale air out.
As an Amazon Associate I earn from qualifying purchases.
A balanced system, often called HRV or MVHR, supplies filtered outdoor air to bedrooms and living areas and extracts indoor air from kitchens, bathrooms, laundry rooms and other service spaces. The two air streams pass through separate channels in a heat exchanger. Heat passes through the exchanger material from the warmer stream to the cooler one, while the supply and exhaust air remain separate.
In winter, that transfer preheats the incoming air before it reaches occupied rooms. It reduces the heating needed to compensate for ventilation losses, but does not turn the ventilation unit into a furnace or air conditioner. The International Passive House Association explains that the aim is plentiful, nearly room-temperature fresh air, and cautions that heat-recovery ventilation should not be confused with air conditioning.
Popular on Amazon
- Ergonomically Designed: Work in tight areas with a compact design that gets into tough spots
- Both tools are designed to fit into difficult to reach spaces
- Complete a wide range of applications with a high-performance motor that delivers up to 300 UWO, and an impact driver delivering up to 1,400 in-lbs of torque
- Both the DEWALT impact driver and drill driver feature integrated LED work lights with a convenient 20-second delay, ensuring enhanced visibility in dimly lit or challenging work areas
- One-Handed Loading - Keep one hand free with a 1/4 in. hex chuck that accepts 1 in. bit tips
Why does a highly airtight home need mechanical ventilation?
In a leaky building, outdoor air may enter through gaps, but those flows are difficult to control: a room may get too little fresh air, while drafts and heat loss occur elsewhere. Airtight construction makes the ventilation strategy more predictable, but it makes a planned ventilation system important for maintaining indoor air quality.
With balanced ventilation, the system’s supply and extract paths are designed to work together. Air moves from the supply rooms toward the extract rooms, commonly through door undercuts or transfer grilles. This lets fresh air reach occupied spaces before it is drawn out from rooms where moisture and odors are more likely to originate. The routes are not interchangeable: putting an extract point in a bathroom does not supply fresh air to a closed bedroom.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteVentilation rates still need to suit the building and its occupants. The association’s guidance says fresh-air delivery should not exceed 30 m³ per hour per person to avoid excessively dry air. This is guidance, not a universal setting for every room or operating condition; the design and commissioning should account for the dwelling and its planned occupancy.
How does the heat exchanger transfer heat without mixing the air?
The exchanger contains separate passages for outdoor supply air and indoor extract air. As the streams travel through the unit, heat crosses the material separating them. In a properly functioning system, this is heat transfer between air streams, not a deliberate mixing of stale extract air into fresh supply air.
There are several exchanger families, including fixed-plate cores, rotary wheels, heat pipes, runaround loops, thermosiphons and fixed-bed regenerators. They differ in how they move or store heat and, in some designs, moisture. ASHRAE distinguishes sensible-only heat recovery from enthalpy recovery, which can also transfer moisture. The type that suits a home depends on climate, humidity strategy, hygiene, pressure drop, frost risk, acoustics and the available test data.
Also popular on Amazon
- Valued Carpenter Pencil Set: You will get 2 pcs solid carpenter pencils with 26 piece 2.8 mm refills, 1 replaceable sharpener, 1 plastic storage box.The complete carpenter pencils combination allows you to finish your work faster and more easily
- Deep Hole Marker Pencil: The deep-hole construction pencils adopts 45mm elongated tip design, which is more convenient to mark in the small hole or in other tight areas that other carpenter markers cannot reach
- Carpenter Pencils with Sharpener: The sharpener is screwed into the top of the work pencil, which won't get lost either. Built-in pencil sharpener that keep the lead with pointed and smooth to Improves line of sight in fine work
- Stronger Solid Lead: This work pencil is matched with a 2.8 mm thick lead , which is much thicker and stronger during the drawing process of construction work, it will not break or damage easily
- Marks on Various Surfaces: 3 colors solid construction pencil can marks on various surfaces,such as metal, plastic, wood, paper etc. Ideals for woodworkers, contractors, craftsmen, builders, merchants and masons
Some systems include a bypass that changes the route around the heat exchanger when heat recovery is not wanted, such as when conditions make cooler outdoor air useful. Whether and how this function operates depends on the particular unit and its controls. It should be included in the design and commissioning checks rather than assumed to work in the same way on every system.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
What is the difference between HRV, MVHR and ERV?
HRV usually means heat-recovery ventilator, while MVHR means mechanical ventilation with heat recovery; both terms commonly describe a balanced ventilation system that transfers sensible heat between the supply and extract streams. ERV, or enthalpy-recovery ventilator, refers to a system that transfers sensible heat and some moisture.
That moisture transfer can matter where indoor humidity management is part of the design, but it is not automatically better for every Passive House. Climate, occupant needs, hygiene, frost behavior and the ventilation strategy all influence the choice. Passive House certification criteria focus on tested performance and other system requirements, rather than requiring one exchanger family for every building.
A central system uses one ventilation unit connected to ducts serving the dwelling. A decentralized or single-room system puts units in individual rooms or façade locations. Single-room systems can be appropriate in some situations, but their airflow paths differ from a whole-house ducted system. The Passive House Institute’s single-room ventilation criteria recommend demand control, since the central system’s overflow path from supply rooms to extract rooms is not available in the same way.
How much heat does a Passive House HRV recover?
The Passive House Institute’s 2025 criteria for certified cool-temperate ventilation units require effective dry heat-recovery efficiency above 75% under balanced-flow test conditions. The same greater-than-75% threshold applies to the cited single-room system criteria. For cold and arctic renovation climates, the Institute’s renovation criteria specify 80% effective dry heat recovery. These are certification thresholds for defined test conditions, not a promise that every installed system will deliver that percentage in everyday operation.
Also popular on Amazon
- 【Great Compatibility】This Katerk 1/4 inch hex shank bit holder is specifically designed for 1/4 inch hex shank drill bits. It's compatible with most 1/4 fast hex handles, hex sockets, various electric screwdrivers, and handheld screwdrivers. The bit holder makes it a valuable addition for any handyman.
- 【Secure and Safe】Built with a secure backup nut design, each drill bit holder securely locks onto your bits, ensuring they stay firmly in place. Additionally, our bit holder incorporates a high-quality steel ball rolling design that holds up to several kilograms of weight, ensuring your various drill bits don't fall off.
- 【Easy One-Handed Operation】The bit holder for impact driver allows you to change bits single-handedly, simplifying your workflow. Its multi-color design further allows for quick identification of the drill bit you need.
- 【Compact and Convenient】Thanks to its compact size, this 1/4 inch bit holder is easy to carry around. The bit holder allows for easy attachment to various tools, making this a convenient addition to your construction accessories. The Katerk bit holder is cast from high-quality alloy material, promising a long product lifespan. Despite its rugged strength, the bit holder remains lightweight, making it portable.
- 【Cool Christmas Gift For Men Stocking Stuffers】 This screwdriver bit holder, driver bit holder, impact bit holder, can be given as a gift to your loved one, especially for anyone involved in construction or electrical work. It's a must-have for stocking stuffers for men and women, tools gifts for dad, tech gadgets for men, gifts for dad, gifts for him, gifts for husband, gifts for boyfriend, cool gadgets for men, and cool gifts for dad.
The Institute’s building-automation guidance describes up to 90% of heat being retained in the building. Treat that as an upper-end figure, not a guaranteed outcome for any unit or home. The actual effect on a building’s heating demand is not the same thing as an exchanger efficiency figure: it also depends on ventilation rates, weather, heat losses elsewhere and how the installation operates.
For its current ventilation guidance, the association gives a maximum electrical consumption of 0.45 Wh/m³ of ventilated air. That figure is important because the fans use electricity, and a heat exchanger’s headline percentage alone does not describe the system’s operating energy. The net-efficiency calculation includes auxiliary fan electricity and frost-protection or defrost energy, so those figures should be considered alongside heat recovery.
When comparing units, check that figures come from comparable test methods and conditions. Useful evidence includes effective dry heat recovery, electrical demand at the intended design flow, test data for the relevant climate and information about frost protection. A percentage without the test basis, flow balance and operating assumptions can give a misleading impression of real-world performance.
What determines real-world performance?
Even a high-performing unit can underdeliver if the system is poorly designed or commissioned. The key factors are:
- Balanced flows: Supply and extract quantities need to be close to the room-by-room design values. The PHI’s cited cool-temperate criteria limit end-of-test mass-flow imbalance to 10%; project commissioning should verify that the installed system is balanced.
- Fan electricity and pressure drop: Undersized or restrictive ducts can make fans work harder. Unit efficiency should be considered at the flow and pressure conditions the home actually requires.
- Frost protection: Cold conditions can require measures to protect the exchanger from frost. Their energy use affects net performance, so compare frost-control information as well as the heat-recovery figure.
- Duct routing and leakage: Ducts routed through unconditioned areas can lose heat, and leakage can reduce the air delivered to rooms. Keeping ducts within the thermal envelope where practical and addressing penetrations helps limit these losses.
- Filter condition: A loaded or incorrectly fitted filter can increase resistance and undermine airflow. The correct filter must fit and seal as specified for the unit.
- Acoustics and serviceability: Noise, accessible filters and the ability to service components influence whether the system can be operated and maintained as designed.
What should be planned during installation and commissioning?
Coordinate ventilation with the airtightness work, not as an afterthought. The association’s retrofit guidance advises installing ventilation after envelope upgrades have achieved the required airtightness, while warning that delaying ventilation after airtightness work can lead to poor indoor air quality.
Also popular on Amazon
- Toolwiz 17-inch magnetic sweeper maintaining a load capacity of up to 8.8 pounds provides a perfect solution to the problem of clearing small ferrous metal objects, such as nails, tacks, bolts, and metal shavings from workshops or garage floors.
- Convenient and portable：17” is good for home, small workshop, or small yard as it is space-saving and more reachable for narrow areas. Perfect for collecting nails or small parts in the car, under the table, and in other nooks or crannies.
- Upgraded Handle Design: The handle features a sturdy, non-telescopic design to completely prevent slipping during use. By simply adding or removing the extension poles, the height can be adjusted to 3 different lengths: 18.9" (48 cm), 32.5" (82.5 cm), and 42.5" (108 cm) from ground to top. This customizable height helps prevent back bending and muscle strain, making your cleaning tasks effortless
- Flexible wheels: Upgrade wheel screws to avoid being too tight to spin or too loose. More comfortable 3-inch rubber wheels roll smoothly on carpet, grass, concrete, and hardwood floors. Just push and pull this rolling magnet-sweeper to pick up metal nails easily.
- Lightweight materials: The magnetic nail sweeper's compact and lightweight design makes the sweeping can be done anywhere you want, Push or pull it under the furniture, passing through the workshop floor, driveway, mud, grass, and gravel.
- Coordinate the envelope and penetrations. Plan duct routes and wall or roof penetrations alongside airtightness work. Keep ducts within the conditioned envelope where practical, and insulate penetrations to avoid thermal bridges.
- Design for the required room flows. Identify which rooms receive supply air and which extract it. Size ducts and silencers for the intended airflow without excessive pressure drop, and preserve an air-transfer route between the rooms.
- Choose a unit on comparable evidence. Look for published third-party or Passive House Institute test data relevant to the project’s climate. Compare effective dry heat recovery, electrical use, frost protection, acoustic data and operating range using consistent test conditions.
- Make filters accessible. Install the specified filter and ensure occupants can reach it for inspection and replacement. Association guidance identifies a high-quality F7 filter at the ventilation-unit suction point; confirm the required grade and arrangement for the selected unit.
- Commission and document the system. Verify and record room-by-room supply and extract flows, fan power, sound, bypass operation, frost protection and condensate drainage. Check that measured flows are close to the design values before relying on the system for routine ventilation.
In retrofit projects, installation sequence matters because the ventilation demand changes when leakage is reduced. A system sized for the old, leaky envelope may not suit the completed airtight home. The design should reflect the upgraded building and the planned flow rates.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How often should HRV filters be replaced?
There is no single replacement interval that applies to every HRV. The interval depends on local dust and pollen, occupancy and how quickly a filter loads. Check the unit’s instructions and inspect filters regularly; replace them with the specified size and rating rather than relying on a generic filter that may not seal properly or may create excessive pressure drop.
Keep outdoor intake and exhaust grilles clear, and check that condensate can drain as intended. If airflow changes after a major duct alteration or filter change, have the flows checked again. Routine filter maintenance is not a substitute for commissioning, but it helps the system continue operating close to its designed airflow.
Recommended Free Tools
Does an HRV heat the house or replace air conditioning?
No. An HRV recovers heat that would otherwise leave with exhaust air and transfers it to incoming outdoor air. It reduces ventilation-related heat loss but does not create heat; the building still needs its planned heating system. Nor is heat-recovery ventilation a cooling system: it supplies fresh air and heat recovery, not the dedicated cooling capacity of air conditioning.
Similarly, humidification inside the ventilation unit is discouraged in the association’s guidance because of hygiene concerns. If indoor air feels too dry, do not assume that adding moisture inside the unit is the right remedy; first consider the system’s airflow and the building’s humidity strategy with a qualified designer.
Also popular on Amazon
- APPLY TO MOST DRILLS : 6 pieces screw extractors work with any drill and all the screw size or bolt (3-12mm), These extractor tools are used to reverse the damaged screw counterclockwise until it is released
- The DIY Tools for Men-Men won't know they need screw extractor set until they have one! This screw extractor set is GIFTS WRAP AVAILABLE, can be gifted to your loved ones as it reflects a fresh trend with fun and practical. Amazing and Unique tool gifts for men women. The must have stocking stuffers for men, gifts for dad, husband, father, him, guy teens, adult, Boyfriend, son on Birthdays, Christmas, Fathers Day or anniversary. Perfect Holiday Gifts Guide
- HIGH QUALITY - This damaged screw remover tool kit is made from High-Speed Steel H.S.S 4341# , which have high hardness of 63hrc, it's durable and easily to remove any damaged screws.
- EASY TO USE: Just two simple steps to get the job done - drill a hole with a cutting size using the right size screw extractor and easily remove the screw or bolt using the removal tool Hardness 63-65HRC: Titanium hardened steel material, more durable than most screw extractors on the market, better hardness and durability than others, buy with confidence and complete peace of mind
- Cool Gadgets for Men Dad Christmas Birthday Gifts for Men and Women - Men won't know they need screw extractor sets until they have one! Every screw has the potential to rust and break, which can create a situation where it cannot be removed. Owning it, there will be no anxiety about rusty screws. This screw extractor set is GIFTS WRAP AVAILABLE, can be gifted to your loved ones as it reflects a fresh trend with fun and practical. Amazing and unique tool gifts for men women. A must have stocking stuffer for men on birthdays, Christmas, Father's Day or anniversaries, a gifts for dads, husbands, fathers, him, adults, boyfriends, sons. The best and most practical and surprising Christmas gifts
Frequently Asked Questions
Can I open windows if my Passive House has HRV?
Yes. Opening a window for a particular reason is different from relying on window opening as the home’s planned ventilation strategy. If windows are frequently open, the heat-recovery system cannot recover heat from the air that bypasses it.
Can one central HRV serve a multi-storey Passive House?
A central unit can serve a dwelling through a planned duct network, but the answer depends on the building layout, duct routes and required room flows. A designer should confirm that the ducts can be routed, insulated and balanced appropriately for the whole home.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteShould the HRV run continuously?
Balanced ventilation is intended to provide ongoing fresh-air supply and extract, with controls adjusting operation as the system design allows. Avoid disabling it for extended periods without professional advice, particularly in an airtight home.
Is an HRV filter the same as an F7 filter?
F7 describes a filter grade mentioned in the association’s guidance, not a universal replacement size or a guarantee that any F7 filter suits a particular unit. Check the unit documentation for the exact dimensions, grade, frame and airflow direction.
