A gas fitter does the gas piping and gas service to your home heating equipment. In many cases the Gas Fitter installs boiler, fireplaces, furnaces, and split system heating and cooling equipment where gas and electricity is used. Alway use a certified gas fitter for any installations of products that have combustable bi products. A gas fitter must know about ventilation of these potential hazardous fumes. If improperly installed carbon monoxide could cause serious health issues and even death. You can always ask to see a gas fitters certificate.
Don W. McAdam Ph. D., P.Eng.
So your floors are cold. What can you do about it?
If you ask at your local building store, look on the internet or ask many contractors, they will tell you to put insulation under the floor. This is not good advice. If you followed this advice you would have the cost of the insulation and installation, an increase in your heating bill and your floors would still be cold. Putting insulation under the floor is not the solution. Sound crazy? Read on and I will show you why a floor is not a ceiling turned over, and how to get your floors warm.
The reason heat is transferred is simple, a temperature difference. No temperature difference equals no heat flow. The larger the temperature difference the more heat is lost. As long as there is a high temperature and a low temperature heat will flow. We cannot change this but we can reduce how much is lost. But you must know how heat is lost before you can do anything about it.
There are three ways (or modes) heat is transferred: conduction, convection, and radiation, and the method of reducing this heat transfer is different for each one. All three modes can act simultaneously, however, in many cases one mode predominates.
Conduction requires a medium, which can be a fluid or a solid. There is no conduction in a vacuum. The thickness of the material and thermal conductivity are important. Thermal conductivity (k, BTU/hr ft °F) is a property of the material and values are tabulated.
The familiar way of classifying insulating material is the R -value (thermal resistance) which depends on material and the thickness.
R = thickness of the material/ thermal conductivity
The lower the thermal conductivity (k) the higher the resistance for a given thickness. For given insulating material increasing the thickness increases the resistance and reduces heat loss.
Typical values of thermal conductivity for some materials and the thermal resistance are
There is a direct relation between heat loss and temperature difference and heat flow can be found using the relationship:
where R is the resistance.
Convection requires a fluid. Heat is transferred by convection when a fluid, liquid, or gas moves. There is no convection in a vacuum. The movement can be “forced”, with a fan or pump, or it can driven only by density difference (“free” convection). Hot air rises because the density of hot air is less than that of cold air.
Convection heat transfer is more complicated than conduction. It depends on:
fluid properties, density, specific heat, conductivity, to name a few fluid velocity, which can be forced or free geometry, the direction of heat flow, horizontal or vertical (up or down)
It is characterized by a heat transfer coefficient (h, BTU/hr·ft²·°F) (also called film coefficient) which depends on many variables. Heat transfer coefficients must be calculated using correlations based on experimental results.
Heat transfer per unit area (BTU/hr·ft² ) is given by:
Heat transfer coefficients for air are low, and those for free convection are very low. Some typical heat transfer coefficients (h) for free and forced convection are:
Free convection for outside surface of a horizontal 6″ heating duct in a room at 70 °F
1 – 3 BTU/hr ft²·°F
Forced convection for inside surface of a 6″ heating duct, depending on velocity
5-10 BTU/hr ft²·°F
inside surface for heating water flowing in a 2″ pipe
~2000 BTU/hr ft²·°F
Unlike conduction and convection nothing but a temperature difference is required for radiant heat transfer. Any two surfaces at different temperatures exchange heat by radiation. Radiant energy can be transferred in a vacuum.
How much is heat is exchanged depends on:
temperature of each surface
geometry, how one surface is “sees” the other.
There are other factors that influence radiation heat exchange, for example the wavelength of the energy being emitted from each surface.
Suffice to say that any surface radiates energy. The hotter the surface the more energy it emits.
How Do These Modes of Heat Transfer Apply
Comparing heat transfer from a floor to heat transfer in a wall and a ceiling will show how they differ. The same modes of heat transfer apply to all three.
The direction of heat flow through a wall is horizontal. Heat flows through the gyproc by conduction. Since the gyproc is hotter than the outer surface it radiates energy through the air space to the outer wall. Heat is also conducted through the air even though it is not a good conductor of heat. (There is also heat transfer through studs, which is conduction, but this is not considered here.) The resistance of a 3 ½ inch air space is about 19. So why would R-14 insulation be used in a wall?
Because hot air rises. Air at the inner surface is heated and rises due to density difference. Air at the outer surface is cold and falls so there is circulation in the wall cavity. Adding insulation in the wall cavity eliminates this air movement. Insulation also prevents radiation because the hotter inner surface cannot “see” the colder outer surface. The predominant mode of heat transfer in an uninsulated wall is convection and this can be eliminated by adding insulation so air cannot circulate. The predominant mode of heat transfer through a wall then becomes conduction. Note that the thermal conductivity of glass wool is slightly higher than that for air. The glass wool prevents air from moving.
Heat flow is up at a ceiling. It is conducted through the ceiling into the attic which is at a lower temperature. Adding insulation above the ceiling, increases the thermal resistance and reduces heat flow. The thickness of this insulation in an attic can be large enough to reduce to the temperature of the top surface sufficiently so there is little or no convection loss to the attic. Air at the top surface is close to attic temperature so air movement is minimized. The predominant mode of heat transfer for an insulated ceiling is conduction. There is radiant transfer from the upper surface of the insulation to the roof however the temperature difference between the insulation and the underside of the roof is small it can be neglected. This radiant heat transfer can easily be reduced however.
The difference between a floor above an unheated space (a crawl space or a garage for example) and a ceiling is that the hot surface is above the cold surface and heat flow is down. A floor is NOT a ceiling turned over. Consider how the three modes of heat transfer apply to a floor to see why.
The air immediately under the floor is hotter than the air space below (a crawl space). This is a stable situation. Hot air rises, but this air has no place to go. Even if there are holes in the floor the temperature above the floor is higher than the temperature under the floor (air density above the floor is less than that above the floor). Air can leak out the edges and this would cause air to move toward the edge (slowly) but this does not have much effect because the heat transfer coefficient is so low and it can be eliminated by sealing the rim joist. Convection can be eliminated.
Heat is conducted down from the floor through the air but air is a good insulator. This is similar to an uninsulated wall but there is no circulation below a floor. The R-Value of 9 1/2 inches of air is about 50. We cannot do anything about this conduction loss but adding insulation makes it worse. We cannot reduce conduction loss to zero but a thermal resistance of about 50 is not bad, and it is free. Heat loss from the floor joists can be practically eliminated. This will be discussed later.
Installing R-24 insulation under a floor reduces the resistance from 50 to 24. Halving the resistance doubles heat loss. This is not a good thing to do. Batt insulation prevents air movement, but in this situation there is no air movement, unlike a wall cavity, where heat flow is horizontal, or an attic where heat flow is up. (A thermal resistance of 50 can be achieved by adding insulation above the ceiling but it is not free.) Insulation is beneficial in both walls and ceilings but it is counter productive when installed under a floor.
The direction of heat flow makes all the difference under a floor. What works in a ceiling or wall does not work under a floor. There is little or no convection and conduction is small, but there is always radiation. Radiation is the predominant mode of heat transfer to an unheated space below. Heat is transferred from the floor and from the floor joist to the to the cooler surface below ( crawl space, garage or another heated space) by radiation. This downward radiation occurs all the time (24/7/365), as long as there is a temperature difference.
Now that we know how the heat is transferred we can do something about it.
Radiation always occurs between surfaces at different temperatures. Heat transfer by radiation from the floor to the crawl space floor cannot be eliminated but it can be greatly reduced and it is very simple to do.
How can radiation loss to the crawl space be reduced? By reflecting it back to the floor. Like light, radiant energy can be reflected by a shiny surface. (technically, a surface with low emissivity (ϵ), a property of the surface). Light is radiation that we can see. A piece of aluminum foil (the kind we use in the kitchen) placed under the floor will reflect almost all thermal radiation back to the floor. Aluminum foil is not practical because it is thin and tears easily, but aluminum foil on each side of a plastic film is available. Stapling this to the bottom of the floor joists will reduce radiation heat loss from the floor by over 90%. This is particularly important if there is an under-floor heating system. This represents a major cost saving since almost all of the energy stays at the floor where you want it. No more cold floors.
Compare radiant heat loss from a floor with, and without, a radiation shield to see how effective it is. Some simple formulae will be used to show how much difference a piece of aluminum foil can make.
Figure 1 Heat flow from floor to crawl space
A simple formula for radiant heat loss from a heated floor to a crawl space floor is
where ϵ1 and ϵ2 emisivities of the floor and the crawl space floor. Emissivity is about 0.9 for these surfaces.
is a constant,
T is the absolute temperature, kelvin (K).
could be called a resistance.
Putting in the numbers for emissivity (0.9) the formula becomes:
Adding a radiation shield below the floor joists as shown in Figure 2 adds another resistance.
Figure 2 Radiation shield below floor joists
The formula becomes:
where εs is the emissivity of each side of the radiation shield.
A typical value of aluminum is ϵ = 0.06. The formula becomes
Resistance goes from 1.2 to 33 and radiant heat transfer is reduced by 96%. Not a bad reduction for a piece of aluminum foil. If there is a heated floor, heat flow down to the crawl space is greatly reduced. The resistance to conduction in the air space is still about 50, which is much better than adding R-24 under the floor.
You can try this by standing below a heat source (a radiant heater is an example) and holding a piece of aluminum foil (from the kitchen) between your face and the heater. Without the foil you will feel the heat. With the foil you will feel nothing.
There are two parallel heat paths through a floor and we have considered only the space between the floor joists not the joists, usually 2 x 10. Wood has a low thermal conductivity, but does conduct heat through the joist where it then radiates to the crawl space. If reflective film is stapled to the bottom of the joist (as shown in Figure 2) there will still be a significant reduction in heat transfer, however, the loss below the joists will still be higher than between the joists. This is because one side of the reflective film is in contact with the bottom of the joist and does not reflect anything. Only the side facing the colder surface does any good. This is easily fixed by leaving a small space between the bottom of the joist and the film. Running the shield perpendicular to the joists and stapling it only at the edges will a give an air space under the joists. A small air space is all that is needed. Figure 3 shows how this can be done.
A radiation shield is simple to install under the floor joists. Unroll it and staple it on as shown in Figure 3. It is also inexpensive. The cost for material was $0.20 per square foot.
Figure 3 Installation of shield to reduce loss from joists
The same technique can be used with a radiant floor installation to prevent heat flowing into the room below or a garage ceiling. A heated basement room would be heated both from above and below, and the room above would get less heat. In this case the radiant barrier should be stapled between the joists and close to the floor above to be most effective.
Figure 4 Installation of shield between joists
The shield is not installed on the bottom of the joists in contact with the ceiling because it is not as effective as putting it between the joists as shown. Only the top surface of the shield would be effective. The “low ε” side in contact with the ceiling would be rendered completely ineffective because it would be in contact with the ceiling.
Figure 5 shows an installation of a radiation shield correctly installed under a heated floor.
Figure 5 Radiant shield over a crawl space
© Don W. McAdam 2012
When looking for a quality bathroom renovation we have found the professionals at Bathfitters.ca to be the right choice. At the Bathfitters.ca company they only do complete tub and shower installations. And the Gas Fitters and Plumbers in GasFitter.ca handle the plumbing accessories.
Let the tile installations and finishing work to be done by Bathfitters.ca
You will get a brand new Tub and complete surround that will last a life time. There is no compromise with materials or fit and finish. Bathfitters.ca has drywall repair people on staff and will handle the complete bathroom remodel to what ever you choose to put in.
We here at Gas Fitter have had a great relation building with us and their clients in Kitchner Ontario.
With Bradley Heating and Cooling you get a HVAC service technician to your door who will take care of your business or home's heating and cooling equipment.
After designing and installing air conditioning systems, heating systems, and heat pump systems, matching with the unique Kitchener climate, we’ve earned a reputation for doing the job right the first time. We have an A+ rating with the Better Business Bureau and have been an accredited HVAC business since 27/11/2009. Our Certified — and our commitment to customer satisfaction — are just two of the reasons we’re rated A+ by the BBB.
Bradley Heating & Cooling they add value to your home and business, they only send Certified HVAC Technicians to your home or office, who have the experience and knowledge to get the job done right from the start.
Buying a water heater is not easy as it seems. Perplexed? Well, there are a zillion varieties of water heaters available in the market and each one of them seems to have the most exquisite features available in the market.
So, how should you choose one out of many? Perhaps, the best thing to do is to rely on a professional for choosing a water heater. He will surely help you out in buying something that you truly need and is within your budget. However, if you wish to buy one on your own then you must know about a few things before finalizing one.
Here are a few points that you must always keep in mind while purchasing a water heater:
1. You must figure out as to what your requirement is. Do you need to boil water in large quantities? What is the frequency for requiring boiled water? Once you have ascertained your needs, it will be much easier to select the heater.
2. Ascertain as to which kind of fuel you would want the water heater to run on. It could run on natural gas, electricity etc.
3. Ascertain the space that you would allocate for the water heater.
Do you have a fireplace at your home? If you have, then you must consider buying a few fire place accessories. Well, if you think it is all about aesthetic appeal then let me tell you, it is much more than that. Fire place accessories have specific use and thus, are more or less required.
Here are a few must have fire accessories:
1. Chimney cap: It is the most essential fire place accessory. A chimney cap is required to ensure that a fire causing item does not fly up to the roof and cause a great fire. Leaving aside that, it also ensures that cold air does not seep into the room from the chimney.
2. A fire door: A fire door protects the family members. It ensures that coal, ash, smoke and embers do not spew out from the fire place.
3. A chimney brush: This is yet another important fire place accessory. It is essential to keep the chimney clean and in order to do so, you need a durable brush. Thus, you must have an adjustable brush for cleaning the chimney.
4. A chimney pipe: It is essential to not let toxic gases and dust to blow in the house; it lets it off into the outside air.
Natural gas is not available everywhere. Thus, it is necessary to rely on a heat pump for your heating needs at such places. However, a heating pump cannot suffice your entire heating needs. Rather, it might not be economical as well. Why? Well, most of the heat pumps run on electricity but when the temperature fall below 45F, then other sources such as gas, wood and oil must be considered. Leaving aside that, a gas heat pump is much more economical and ‘easy on your bills’ as compared to an air conditioner.
The best thing about a heat pump is its utility. A heat pump can not only be used to heat your home in winters but it is equally effective in cooling the place in dry arid summers. Isn’t that great! Thus, it is an ideal choice for making your home a cosy place to live in.
How do the heat pumps work? Well, a heat pump uses a fluid to transfer the heat from one source to the other. For instance, it will absorb the heat from one air source and transfer it to the other. Air conditioners also work on similar process but they cannot be used all round the year—heat pumps can.
It is necessary to maintain your air conditioning system. Many people do not pay attention to the air conditioning system as a result of which they face problems later on. They have then no other option but to call an AC repair professional and thus, they end up shelling out huge amounts of money. Leaving aside the efficiency factor, there is one more factor that is directly related to the maintenance of air conditioning system. It is health factor. If the AC is not cleaned/ maintained regularly, you are bound to face health problems as unclean AC circulate dust everywhere.
Here are a few tips for ensuring a higher efficiency of your air conditioner:
1. Close the windows and draw the curtains: Windows are bound to lower the temperature by 10-15 degrees and thus, it is advisable to close the windows and draw the curtains when you are turning on the air conditioner.
2. Do you know 25% of cooling is lost due to leakage and cracks in doors and windows? Yes, it’s true! So, if you wish to increase the efficiency of your air conditioner without raising electricity bill, you must fix the cracks in doors and windows immediately.
Every one of us faces gas fitting issues in our homes. Whether we face it once in a year or once in a month but we do face it and when we do, we rely on an experienced professional i.e. a gas fitter to fixing the problem.
Gas appliances and heating systems are pretty complicated and thus it is rather appropriate to contact a gas fitter to fix the problem. However, not all gas fitters are good enough/trained enough to fix it correctly. Thus, it is necessary to find a reliable gas fitter before handing him over the home keys.
Here are a few tips that can help you with finding a reliable gas fitter:
1. Credibility: You must check the credentials of the service company. If you think they are not divulging you the details of their licence and information of previous customers, chances are that they are charlatans. Steer clear from such people.
2. It is imperative for you to know whether the gas fitting company has sufficient knowledge and experience in fixing related problems or not.
3. You must take references from your neighbours, family and friends about a reliable gas fitter.
What is an HVAC? An HVAC is a heating ventilation and air conditioner system. It is installed in homes to provide heating, ventilation and most importantly air conditioning for the family. It is necessary to do a bit of research before choosing an HVAC as there are many HVAC systems available in the market. However, it would be great if you can hire an HVAC installation service provider for choosing the one for you.
Here are a few benefits of hiring a professional for guiding you to buy an HVAC system:
1. It is important to note that every model of HVAC system has specific requirements. It would be a wild goose chase if you are looking for ‘one size fits all’ HVAC system. A professional can help you in understanding your needs and choose one that is most suited for your needs.
2. A professional can also help you in ascertaining whether your old HVAC system can be modified and turned into a new one or not. If it can be done, you will surely be saving a lot of money.
3. A professional can help you choose an HVAC system that fits in your budget.