Learning about ducted heating systems helps you fix energy efficiency
As a youngster you would have heard your mother shout, ‘You don’t live in a tent, do you!’ referring to leaving a door open to outside. Well, there just might be some benefits with leaving your bedroom door open concerning the efficiency of your ducted heating system. Read on.
We never seem to be able to explore and utilize the full potential features of new and unusual wiz-bang technology that we use to entertain us and keep us comfortable in our homes these days.
Ducted heating systems surprisingly are one of those devices that we assume we know how to use, but due to them being designed and implemented for accommodating the whole home it can have a detrimental effect on its effectiveness as we live our day to day lives.
The Main activities that harm ducted heating energy efficiency are the following:
- Closing off ducted heating outlets to reduce the overheat energy necessary for unused rooms/or parts of the home. This can elevate the supply air temperature inside your ducts, damaging the duct tape holding your ductwork together.
- Closing doors to bedrooms when ducted heating is running. This forces warm air leakage to outside.
When a Ducted heating system is unrestricted, and all pathways are open for air to move to the return air vent freely, all is well. All the doors are open and “Green”.
This recirculation of conditioned air is called a Closed System and is much more efficient than forcing it to escape outdoors. What is supplied, is returned on the opposite end.
Due to ducted heating systems being a closed system, closing doors or closing floor vents affects the efficiency of a home, because of the restriction to air returning to the Return Air vent. In diagram 2 the “Red” doors are the ones which are closed.
When supply is restricted from getting back to the return, the area of the house that is open to the return air outlet goes under negative pressure sucking cold air from outside, while the rooms which have supply vents with closed doors, go into positive pressure pushing hot air outside via evaporative cooling vents/leaky windows or wall vents if they exist.
The thermostat in the central area close to the return air vent gets exposed to cooler outside air temperatures, while the rooms with closed doors, overheat as the crippled ducted heating system tries to work harder and longer trying to heat the area which is under negative pressure.
Depending on how restricted the ducted heating system is on the supply side, decides what the energy overhead ends up being.
There is an additional potential cost via the return air supply vent:
If your return air outlet is not very air tight, open to a wall cavity, which in turn is connected to your subfloor or loft area, air will be bypassing your filter and drawing dusty air from your roof into the house. This can also encourage creepy crawlies (e.g.,. Whitetails, cockroaches) entering the return ductwork, and be deposited in each room via the many supply vents in the home.
That’s just great isn’t it?!
So, make sure you check the return air vent that could be located in front of a wall cavity. It’s a very common occurrence all over Australia. They need to be boxed in or foam-a-filled.
ecoEVO Episode 3 tested a leaky ducted heating system. click to watch.
Ducted Heating air tightness tested with and without tape installed.
Sooooo, the moral of the story is… Restriction of air from supply outlets should be considered when closing up supply registers in the floor, especially when doors to other rooms may also be closed, which is similar to closing off the supply vent also.
The solution…
Install a door vent in each door that has supply vents installed back to the gas ducted heating system. Allow air back to the return air vent whether the door is opened or closed.
There are many scientific reports and even feng shui documentation out there that talk about, the benefits of sleeping with doors opened or closed.
Feng Shui exert:
Keep all bedroom doors closed when you sleep
According to feng shui principle, leaving your bedroom door open when you sleep allows positive chi to flow out, and opens up your space to negative energy. Sleeping with the door shut promotes feelings of safety and security, bringing you calm and peace of mind.
Feng Shui is great, but it isn’t your best guide to ducted heating energy efficiency so let’s have a look at the actual impacts in a modern house?
Cons of sleeping with a bedroom door open or closed
| Door open | Door closed |
|---|---|
| Less safety if smoke alarms are not installed or working | Reduced air movement (High CO2 Build up) CO2 is heavier than Oxygen. It just hangs around, and it’s not good to sleep in a high concentration. |
| Noise and privacy issues | Ducted heating restriction there for energy efficiency is affected. |
| Improved safety from fire (If ducted heating is not running, Supply air could suck air from the main living area and push it into other rooms via outlets.) | |
| Bedrooms that have open supply outlets with closed doors over heat. |
Conclusion…
Without ducted heating on, sleeping with a door closed can push CO2 in the room up to 4000ppm, which is not ideal for health, and could adversely affect your performance the next day.
Sleeping with a door closed while your ducted heating system is running, can overheat your room, leaving you dehydrated, but it can also be costly.
When you are considering a heating system for your home, consider your lifestyle, and whether you need a device that heats the whole home or just a portion of the home. Don’t count on a ducted heating system to partly warm a home unless it’s a well designed zoned system with a variable fan (even then, be sceptical of the airtightness of the damper that closes to separate zones). For existing ducted heating systems installed, replace the thermostat with one capable of scheduling. That way you will be able to estimate a time when everyone is asleep where doors may be assumed to be closed, and the ducted heating system can be turned off.
The quality of a duct installation can also exaggerate an unbalanced heating system (Holes in your ducts or ducts not taped together correctly). So it may not all be the fault of the occupant.
The ultimate solution…
Concentrate on improving your homes passive ability to keep the temperature in, via the building envelope, (airtightness and insulation consistency), and reduce the chance of your ducted heating system from becoming unbalanced by using door vents. Limit and be aware of how many ducted supply vents you close off at one time. The better the balance, the less your ducted system leverages from the holes in a leaky home.
Other References
http://www.greenbuildingadvisor.com/blogs/dept/musings/return-air-problems
By John Konstantakopoulos
