We all want ways to save energy but how?
As a “Smart Home” technology professional I meet homeowners all the time, perhaps when they are self-building their family home; renovating a room or whole house or simply interested in ways to save energy.
During our time, we discuss Smart Home features such as lighting control, heating control and motorised shading and elude to benefits including ways to save energy without backing up the statement with factual evidence or at least some science behind the claims.
The aim of this article is to look in to the ways to save energy using Smart Home solutions.
But how much energy do we use?
We (or you) could of course, calculate the surface of your property’s exposed external walls and then calculate the u-values of each element using Standard Assessment Procedure (SAP) methodology. Calculating the ventilation losses dependent on the cubic volume of each room and the air changes per hour through open windows and other forms of infiltration before calculating the annual space heat demand taking into consideration the degree-days (the number of days when the average outside temperature is lower than a base temperature above which a building needs no heating) based on your geographical location in the UK. Then comparing the different efficiencies between the different types of spacing heating to calculate total energy consumption….
The Department for Business, Energy & Industrial Strategy publish statistical information each year on the Energy Consumption in the UK. The latest Domestic final energy consumption by end use, figures show;
|Thousand tonnes of oil equivalent (ktoe)||Space heating||Water||Cooking||Lighting||Appliances||Total|
|Bioenergy and Waste||1,556||532||-||-||2,088|
We all consciously want to be “green” and reduce our impact on our planet. We may believe we are doing our bit by spending an extra minute or so, sorting our refuse into recycle-able and non-recycle-able materials every day whilst at the same time ignoring the same level of effort to turn down our home’s thermostat when we leave our homes each time we go to work. We could probably calculate the equivalent tonnes of oil our recycled cereal box has saved the planet but let’s assume, our recycling efforts would not amount to 25,579 thousand tonnes!
Selfishly, our interest in being “green” is also more about saving our money than on our planet. If we accept this and financially quantify the above figures in relation to the impact on our pockets we need to know what we spend on our energy bills. According to ofgem, in the period between November 2014 and October 2015, the annual average dual fuel customer bill in the U.K. was £1,326, resulting in a breakdown as follows:
Probably unsurprisingly in the UK, at 70%, space heating is the biggest consumer of energy in domestic properties, so this seems an obvious place to start to investigate ways to save energy (our money).
Space Heating and ways to save energy
Now we know how much energy we use and how much it costs to heat the spaces in our homes, we need to look at what spaces to which we are referring. Because we are discussing ways to save energy in domestic properties we obviously know the spaces cover living rooms, kitchens, bathrooms and bedrooms. But is our £922.96 paying to heat a one bedroom flat or a six bedroom mansion per year?
According to (Royal Institute of British Architects ) RIBA (The Case for Space: the size of England’s new home, RIBA, September 2011) a survey of a sample of 3,418 homes across 71 sites concludes that an average three-bedroom home has an internal floor area of approximately 88m2.
The most common type of dwelling here in the UK is a three bed semi-detached property – with 2-3 occupants. The average home comprises of a living room, kitchen, bathroom and 2 or 3 bedrooms. The average home tends to have been built from solid brick 220mm walls (instead of cavity walls), double or single glazing with modest loft insulation and some form of central heating system.
Although our statistics are not correlated, it is fair to assume, for our purposes that the average UK energy bill is used to heat the average and most common UK dwelling.
Where a Smart Home (or Smart Home professional) provides ways to save energy is neither in the selection of the building’s materials, nor the method of the construction, or even to a degree (excuse the pun) in the sources of heating but more in the way the energy is used (controlled) when the property is occupied, given whatever efficiencies or lack of efficiencies the property provides. This means the savings discussed in this article apply to both new builds and existing homes alike.
Conventional method of Space Heating
Before looking at the Smart Home approach, let us first look at how the space heating in our average three-bedroom home is conventionally controlled.
For as long as central heating has been around, homes have had just one thermostat located centrally in the property. This location, typically a draughty non-habitable hallway, measured the temperature in the hallway and only in that hallway. When the temperature of the hallway reached the random desired temperature i.e. “set point”, an internal “relay” in the thermostat would open and break the electrical supply to wiring centre where zone valves would then close and the demand to the heat source, let’s assume, a gas fired boiler would stop.
Using this method and assuming all radiator valves were permanently open, hot water heated by the boiler would be pumped around ALL radiators. Radiators would continue to heat the rooms through radiated heat and would continue to do so until the hallway reached the desired temperature. This would mean the temperature of each room would be random, based on the efficiency of the radiator and the speed at which the generated heat is lost.
Optionally, at each radiator, a Thermostatic Radiator Valves (TRVs) could be used allowing a crude level of individual control of the room’s temperature but heating would still be demanded given the heating demand for the whole house is controlled from the central hallway thermostat not the TRVs.
The only way to “turn off the heating” would be to lower the “set point” of the thermostat in the hallway to a random setting, often to the lowest possible setting or by going around each radiator and doing the same. Let’s face it, at best, someone who was very energy conscious may perform the former process each time they left the property but generally speaking it just wouldn’t happen.
Some central heating systems used a time programmer to define a schedule for both heating and hot water. The schedule would help by ensuring the heating was not on between a set period, typically, during working hours Monday to Friday but it would never get adjusted other than to change the time at clock changes.
Modern method of Space Heating
The most well-known Internet of Things (IoT) device for heating is the Nest thermostat, shown below. Originally invented by Tony Fadell and Matt Rogers former Apple employees who founded Nest Labs in 2010 before being acquired by Google in 2014.
As you can see the Nest Thermostat is more modern looking than a traditional thermostat and now in it’s 3rd generation, the Nest Thermostat even has inter-changeable “rings” to match the interior design of the room. Although a marketable feature what does it technically do and does it give us ways to save energy?
Firstly, it’s an intelligent thermostat. This means it has a PID Controller (proportional-integral-derivative). Without going into depth, the basic idea behind a PID controller is to read a sensor (temperature sensor in thermostat), then compute the desired actuator output (heating demand signal) by calculating proportional, integral, and derivative responses and summing those three components to compute the output.
This means the PID learns how much time it takes to heat the space to a temperature. Knowing this information, which is different in every home, allows it to begin the heating process BEFORE the time on the schedule. For example, if the built-in heating schedule is programmed for 22o degrees between 18:00 and 21:00 and the PID has learnt it takes 1 hour to increase the temperature 1o degree, then if the room was at 20o, the heating would turn on at 14:00 so that the room was 22o at 18:00.
Additionally, Nest market features like knowing when you’re away from the home using sensors and your phone’s location which may or may not appeal to everyone. The feature known by most, following Nest’s extensive marketing, is being able to change temperatures and schedules using mobile devices from both within the house and away. This certainly is a convenient feature and no longer do we need to go to the airing cupboard to adjust schedules, etc.
Does it save energy?
Well they must, as Nest even provide an Energy History report to show how much energy you’ve saved but is it utopia when it comes to ways to save energy?
In our opinion, it’s a start and the marketing collateral from Google is certainly helping raise awareness of such devices. It’s easy to believe Google’s Nest is the only solution and that they want to reduce the world’s energy consumption but there are other ways perhaps which do not involve personal activity monitoring for commercial purposes.
Zoned Heating method of Space Heating
The Nest Thermostat is a great product but it is still only one device located in one room so still analogous to our conventional thermostat in our draughty hallway, albeit more intelligent.
Before we get bombarded with comments, we know Nest can now have multiple devices and the thermostats can be moved but to achieve the zoned heating we will discuss would be difficult with the existing Nest Thermostat solution and in our opinion there are better ways especially when secondary heating sources and/or cooling are required.
Zoned Heating is a solution used by us to provide greater control of the space heating in your home and provide greater ways to save energy. If you think of all the rooms in your home as “zones”. Then imagine you can automatically turn on/off heating in each room independently of each other and not as a whole house, this is effectively “zoned heating”
Let’s go back to our average house according to RIBA with internal floor area of approximately 88m2 and assume it is made up of the following rooms:
|Area (Sq. Meters)|
In order to illustrate the financial benefits of a Smart Home “zoned heating” solution we need to make some further assumptions as to the usage of the property. Given the increase in homeowners working from home, let’s assume that one of the occupants works from home but occasionally needs to leave for meetings. The other occupants are all out of the house between 8am and 4pm Monday to Friday and on weekends all occupants are regularly but not always away from the home.
Let’s also assume the existing central heating is currently controlled by a conventional thermostat in the hallway and the heating is scheduled, for simplicity sake and not uncommon, between 6am and 10pm every day (66% of the week) which costs them the above average of £922.96 in space heating per year.
Looking at just the time period the heating is on (112 hours), 100% of the house is being heated 40 hours i.e. between 8am and 4pm Monday to Friday when only one occupant is in the house. Whereas, the occupant working from home only really needs the Office and the Kitchen/Dining Room heated, equating to roughly 28% of the house between 8am and 4pm Monday to Friday.
|Cost of heating 100% of the house Mon-Fri 8am-4pm||£329.64|
|Cost of only heating 28% of the house Mon-Fri 8am-4pm||£92.30|
Then we have the period 6am until 8am and 4pm until 10pm Monday to Friday (40 hours) when the heating is currently on and all occupants are in the house. Assuming all occupants occupy just the Living Room, Kitchen/Dining Area and want the hallway heated i.e. 50% of the house during these periods.
|Cost of heating 100% of the house Mon-Fri 6am-8am and 4pm-10pm||£329.64|
|Cost of only heating 50% of the house in same period||£164.97|
In our example, a saving of £402.31 per annum (44%) would be made by using a zoned heating solution.
Smart Home method of Space Heating
Once you have a zoned heating solution, it can be integrated and controlled by a Smart Home. Rather than a fixed heating time schedule, “Lifestyles” can be created.
Each Lifestyle would define a temperature set point for each room. The rooms which do not require heating rather than turning “off” the heating would be set to a “frost protection” temperature to ensure they do not get damp. The activation of the Lifestyles could be combined with the setting and un-setting of the home’s security alarm system.
So, in our example above, we would create three lifestyles:
- Lifestyle 1 “Working from Home”
- Lifestyle 2 “Home”
- Lifestyle 3 “Away”
A “Night” lifestyle could also be created
This would be ideal for the above example, where the occupants regularly but not always leave the property over the weekend or for those ad-hoc meetings during the week. Instead of remembering to adjust the heating schedule, they simply set the house alarm and the Smart Home subsequently activates “Away” Lifestyle which in turn sets all rooms to “frost protection” temperature.
If we assume the occupants, in our example, are away one in four of the weekends in a year (25%).
|Cost of heating 100% of the house every weekend 6am-10am||£296.66|
|Cost of only heating 50% of the house in same period for 3 out of 4 weekends||£111.25|
A further saving of £185.41, in theory, could be saved by making it as easy as possible for the occupants to “inform” the Smart Home that they are “Away”, by setting an alarm to activate a “zoned heating” Lifestyle. This could be activated like how Nest use your phone’s location by introducing geo-fencing but in our opinion this is not a recommended method as; are you gone for 5 minutes or 5 days?
Depending on the length of time of non-occupancy and heating system, particularly underfloor heating, it may be more energy efficient to leave heating “on”.
We accept we’ve made a lot of assumptions but we are just trying to illustrate possible ways to save energy.
Obviously, the bedrooms and bathrooms in our example would require heating and have not been considered but equally this is a modest sized property. A zoned heating solution in a larger less occupied property, especially combined with a smart home system could provide even further savings.
We’ve shown an approximate 64% financial saving of £588 per year off a modest property’s space heating cost.
But more importantly, if this was applied to all domestic properties in the UK approximately 17,650 thousand tonnes of oil equivalent (ktoe) precious natural resources would be saved!