Ventilation Case Studies
In this section we share real ventilation case studies from homes across Ireland. Each example shows a common installation mistake, explains the risks for the occupants, and demonstrates how Eco Vent corrects the problem through proper design, installation, and commissioning.
Case Study 1 – Unsafe Condensate Trap Installation
During a service visit we found an improvised condensate trap built from a flexible washing machine hose, loosely connected to a waste pipe and routed beside an electrical connection. This type of DIY fix is unsafe and can lead to leaks, odours, and electrical hazards.
Key issues identified
- Washing-machine hose used as a condensate trap instead of a purpose-designed trap.
- Poor, unsealed connection to the waste pipe allowing potential leaks and odours.
- Condensate pipework routed very close to electrical cabling/connection.
- No visible access for cleaning, inspection, or safe maintenance.
Case Study 2 – Uninsulated MVHR manifolds in cold attic
In this property the MVHR supply and extract manifolds were installed in a cold attic space with no insulation around the manifold boxes or connecting ductwork. As a result, valuable heat was being lost into the attic, reducing heat recovery efficiency and increasing the risk of condensation within ducts.
Key issues identified
- Manifold boxes located fully outside the thermal envelope in a cold attic.
- No insulation to manifold bodies or connections, causing significant heat loss.
- Risk of condensation forming on cold metal/plastic surfaces and inside ducts.
- MVHR not achieving expected efficiency or comfort levels for the occupants.
Case Study 3 – MVHR unit with open condensate outlet
On another site we found an MVHR unit installed with the condensate discharge left fully open and not connected to any drain. During operation, condensate from the heat exchanger was free to drip out of the unit, risking damage to the appliance and surrounding structure.
Key issues identified
- Condensate spigot on the MVHR left open, with no trap or pipework attached.
- Risk of water leaking onto ceiling/attic structure and damaging finishes.
- Potential for mould growth around the unit due to persistent moisture.
- Evidence that the system had never been properly commissioned or signed off.
Case Study 4 – One missing pipe, and a system that couldn’t be balanced
We were asked to commission and balance a Vent-Axia Econiq M heat recovery system in a new house in Co. Dublin. The ventilation design was good, prepared by an established design company. The installation wasn’t: the design gave the utility room two extract pipes, and the builder connected only one.
One pipe can’t carry the utility room’s extract. To get its design airflow, the extract fan had to run about 10 % harder than the supply fan, which pushes the house towards negative pressure, the opposite of what TGD F requires. No valve setting can make up for a missing pipe, so we didn’t sign a commissioning report. The second pipe has to go in before the system can be balanced.
Key issues identified
- One extract pipe to the utility room instead of the two in the design.
- The extract fan needing about 10 % more than the supply fan to reach the design airflows.
- A house that would run under negative pressure, drawing unfiltered air in through gaps.
- A good design undone on site: the number of pipes on the drawing matters as much as the unit.
Case Study 5 – Heat exchanger fitted upside down
During a service visit we found a rust-coloured deposit inside the MVHR unit. It showed that condensate was not draining away properly: the heat exchanger had been fitted upside down. We turned it the right way.
Key issues identified
- Heat exchanger fitted upside down.
- Condensate not draining away properly.
- Rust-coloured deposit building up inside the unit.
Case Study 6 – Air valve fixed with a screw
In this house a ceiling air valve had a screw driven through its centre. With the screw in, the valve cannot be twisted out by hand for cleaning. The flange already holds the valve in place, so the screw does nothing useful.
Key issues identified
- Screw driven through the centre of the air valve.
- The valve cannot be twisted out by hand for cleaning.
- The flange already holds the valve, so the screw adds nothing.
Case Study 7 – Shop-bought pre-insulated duct that came apart
On a service visit in the Midlands we found that the heat recovery (MVHR) ducts in the attic were a ready-made pre-insulated duct set, bought from a shop. One joint had come apart. A bend had pulled off its spigot at the distribution box, under the attic insulation.
With the joint open, the room on that duct was getting little or no air, because the duct was open to the attic instead. From inside the house nothing looks wrong, because the valve in the ceiling looks the same as before.
The duct is made of a light, rigid foam, much like polystyrene. The pieces push together and are held with plastic connectors, and the foam gives screws, clips and tape very little to grip. It is hard to secure, the joints don’t stay put, and in our view a duct like this will struggle to last for years.
We hung the duct again, pushed the joint back together, sealed and secured it with strong tape, and added a metal hanging strap from the roof timbers, so the weight of the duct no longer pulls on the joint.
We prefer rigid duct. It can be fixed and supported properly, its joints stay where they were made, and the insulation goes on around it. For self-builders fitting their own system we cut the insulation to their duct design, 90° bends included, instead of selling pre-insulated duct sets: see our DIY MVHR kit.
Key issues identified
- Shop-bought pre-insulated duct set made of a light, polystyrene-like foam.
- A joint in the attic came apart over time.
- The room on that duct was getting little or no air, with nothing to see from inside the house.
- Foam duct is hard to fix and support, so the joints don’t stay put.