Ducted Heating Energy Efficiency Fix
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 to leaving your bedroom door open concerning the efficiency of your ducted heating system. Read on.
We often fail to leverage the full potential of the new wiz-bang technology we use keep us comfortable in our homes these days. Ducted heating systems are one such device. Although they are designed and implemented for accommodating the whole home, our everyday habits can have a negative impact on their effectiveness.
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 to leak 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. At the same time 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.
There is an additional potential cost via the return air supply vent: If your return air outlet is not very airtight or open to a wall cavity 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) to enter 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 is boxed in or foam filled. This is a very common occurrence all over Australia.
ecoEVO Episode 3 tested a leaky ducted heating system. click to watch.
Ducted Heating air tightness tested with and without tape installed.
So, the moral of the story is… Restriction of air from supply outlets should be considered when closing up registers in the floor. In fact, closing doors in the house has a similar effect to sealing registers.
The solution…
Install a door vent in each door that has supply vents to maintain air flow 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.
An examination of this specific topic and its impact in the modern home can be found below.
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. This can also overheat your room, leaving you dehydrated, and potentially costing more.
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, turning on and off according to your routine.
The poor quality of a duct installation can also exaggerate the problems in an unbalanced heating system. This might be caused by holes in your ducts or tape not holding sections together properly.
The ultimate solution…
- Concentrate on improving your home’s passive ability to keep the temperature in via the building envelope (airtightness and insulation consistency).
- 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 is disadvantaged by air leakage in the home.
Other References
http://www.greenbuildingadvisor.com/blogs/dept/musings/return-air-problems
By John Konstantakopoulos
