# Roof Insulation



## jimclarck (Mar 5, 2020)

Hello,

This is a questions to the "builders" out there... Just bought a house in Aljezur and the survey recommended insulating the space between the concrete ceiling and the roof tiles. There is a "slanted" roof above the levelled ceiling. I have attached a picture to show what I mean.

Any idea what is the best insulation material that can be put on the concrete?
Is is easy to gain access by removing a few roof tiles or in Portugal they cement each tile rather than just the first few rows and last?

Thanks!


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## John and Cecil (Dec 22, 2019)

Hi, I am not a builder in Portugal however I did renovate homes for a living overseas for a long time. The houses are very different though, they were all wood framed with asphalt shingle roofs. It appears that many of the homes here allow you to move the interior roof tiles to access the attic (if there is no opening to access it from within the house). I recently looked a newer house (less than 20 years old) with no internal access from the home to the attic and the idiots installed the water heater (with storage tank) inside the sealed off attic. From what I was told if you need to get to the water heater then you must remove some roof tiles. I asked why they did not put an opening in the ceiling to access the attic and the answer was it was because the attic was insulated (I guess they never saw a small wooden access hatch in the ceiling which you apply insulation to the back of the wood). There appears to be some really incompetent builders and architects here. I have yet to see one whole house fan here which vents out the attic and draws air into the attic from the lower areas of the house. They also don't use window screens much here, yet they have flys and mosquitos.

You have your work cut out for you. If I buy a house here I will be looking into the possibility of cutting a small opening in the ceiling just large enough to allow me to climb up into the attic and also I will use that to enable a whole house fan system.

As for the insulation, perhaps someone with with local experience will know better but I would think you would want to use something like polyurethane closed cell insulated panels and possibly some polyurethane spray foam.


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## Strontium (Sep 16, 2015)

Hi,
May I have more information please?
Who did the "survey"?
How do they know there is no insulation?
Have they inspected the underside of the roof ie under the tiles?
Traditional roof has sealed ceiling and vented roof space so heat from tiles are not transmitted to the interior of the house.

Usually only the edge and ridge tiles are cemented


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## John and Cecil (Dec 22, 2019)

Sealed ceilings? What are they thinking here! We have vented roofs in the USA and nearly all homes have a hatch (even in places in Southern California and Nevada where it gets very hot) where you can access the attic. You want to be able to get inside your attic without having to take your roof apart as if it were a lego house. The hatches are usually covered with a layer of insulation. Attic heat does not really travel down into the house (it heats the ceiling and radiates through it whether it is sealed or not), and whether a ceiling is completely sealed off or if it has an access port that can be opened or closed makes very little difference. Hot air goes up. In the summer when it is hot, especially in the evening when temperatures start to drop you WANT air to flow from the house up into the attic and you WANT to remove the hot air that collects just below the ceiling. 

This is the whole concept of a whole house fan. As temperatures start to drop in the evening you turn on a whole house fan and open some windows where it is coolest outside. It draws the fresh air in down low and pushes that hot air up by the ceiling into the attic, and then pushes the hot attic air outside. A whole house fan will cool a house on a summer evening in just a few minutes and it uses very little power. Surprisingly I have never seen one here yet.

I also highly recommended window screens (thin metal frames covered in fiberglass material that has many small holes which allows air and light to pass through but not insects). It is funny that I feel the need to describe what a window screen is here but I almost never see them here either.


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## John and Cecil (Dec 22, 2019)

Here is another inexpensive device that I do not see used very much here, it is a wind powered roof ventilator wind turbine. I had one on my garage roof in California, it did work but the garage still got very hot. They also make electric powered ventilation fans for use in attics that will automatically turn on when the temperature gets above a certain temperature. I had one of those in my house roof in California. These work well for lowering the attic temperatures during summer days. You can probably put a small solar panel on the roof to run the ventilation fan, which might work well since it is the sunlight that also heats the roof.


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## jimclarck (Mar 5, 2020)

Hi All,

Thanks for the replies. Here is the house drawing. I marked in red color the spaces. The inspection for the insulation was down by the energy certificate people who recommended attic insulation, solar hot water system and mini split AC/heat. The house survey was down by a civil engineer with a MSc in HVAC.
It seems that the only entry into the space will be by removing some roof tiles. I am still trying to figure out what kind of insulation will work best. Some people suggested insulating from the inside (double ceiling) but I think that it's too much work to put drywall all over the ceiling.


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## jimclarck (Mar 5, 2020)

John and Cecil said:


> They also don't use window screens much here, yet they have flys and mosquitos.


I know, it's crazy!


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## John and Cecil (Dec 22, 2019)

Yikes, insulate the inside of the ceiling?  You have a unique roof system though. It is possible an access hatch won't allow you to get inside anyway as it is so small and there are 3 separate compartments. I would have liked to put an extra layer of polyurethane panels under the roof surface however there appears to be no room to work inside the attic. I think I would opt for a heavy layer of insulation on top of the ceiling inside the attics. I would definitely use an insulation that has no chance of growing mold if getting wet, because without access to the attic you will never know if you have a leak (until you start coughing and wheezing from mold exposure).

Also, I am very curious about the section of roof that is not red? That is where you might want to put a layer of insulation inside the house below the ceiling. I guess it depends on how warm that ceiling gets in the summer. Is there a small window way up high near the ceiling in that room? That would be a great place to install a fan to exhaust hot air out of the house and draw air into the lower windows. At least this is what I would be considering based on what I have seen and based on no Portuguese experience 

Also I assume you will be putting the solar water heater tank inside the house and not inside the attic. If you put it in the attic without access then you might want to put a wifi camera up there to make sure it does not start leaking without you knowing about it.


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## jimclarck (Mar 5, 2020)

John and Cecil said:


> Is there a small window way up high near the ceiling in that room?


Yes, there is a window. The house doesn't get really hot in the summer.



John and Cecil said:


> Also I assume you will be putting the solar water heater tank inside the house and not inside the attic.


It's the one with the tank just above the solar collector (siphon system)


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## John and Cecil (Dec 22, 2019)

Oh, the insulation is for the winter I guess. My mind is preoccupied with hot weather at the moment  I think a thick layer of insulation above the ceiling in the attic may be a good idea. Also hopefully you have an efficient heating system that uses pellets /bio or wood. Diesel, propane/gas, and electric heat are all very, very expensive here. I worked it out on paper last winter and diesel, propane, and electric all cost about the same for 1kw of heat but wood pellets cost only 1/3 as much!


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## jimclarck (Mar 5, 2020)

John and Cecil said:


> Oh, the insulation is for the winter I guess. My mind is preoccupied with hot weather at the moment  I think a thick layer of insulation above the ceiling in the attic may be a good idea. Also hopefully you have an efficient heating system that uses pellets /bio or wood. Diesel, propane/gas, and electric heat are all very, very expensive here. I worked it out on paper last winter and diesel, propane, and electric all cost about the same for 1kw of heat but wood pellets cost only 1/3 as much!


The current setup for hot water is a gas (on bottle) tankless heater. The idea is to plumb the solar hot water into the tankless inlet so if we run out of hot water due to clouds the gas will kick in automatically.

As for a heating system, we are looking at a 5 zone multi split. I would have gone for hydronic under floor but the cost of digging all the tiles out and parts of the concrete under it is just too much.
We looked at a pellet stove but the initial cost of the stove plus running radiators everywhere was too much too. There is only a wood stove in the living room right now and I am not sure if the vent above it is just an air vent of a fan coil unit (see picture with red circle).

Would love to hear your thoughts about an economical heating system.


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## John and Cecil (Dec 22, 2019)

What fuel is your 5 zone heating system going to be using? 

One of the problems of these Portuguese houses (without lumber studs) is there is no wall cavities to run things like wires and radiator pipes. Personally I hate having radiator lines run on the surface of walls where they can be seen. I am certainly no expert on heating systems but I have been looking into it here. It was easy in the USA, I always had forced air heat that used natural gas. Natural gas was cheap, my two on natural gas hot water heaters in California (1 was the tank model, the other was tankless on demand) had an $8 bill each month for one person. However utility rates here are several times more expensive. 

It really depends n your house design and layout, as well as how cold it gets there. Your house does not look very old, perhaps it has the radiator lines preinstalled inside the walls. If you have wide hallways or maybe even a closet in the right place (like near the doorways to several bedrooms) you might be able to install a pellet heater in the hallway or inside an alcove. You can also install a pellet heater in the living room or between the living room and say the kitchen. You may be able to open some doorways up to assist in allowing the heat to move from room to room. Pellet heaters are the cheapest and also they are very efficient. Fireplaces however are not, although they do make them with a heat recovery system to make them more efficient which may be what you have.

I assume your 5 zone heating system is going to run on diesel or propane or maybe electric? You are going to want to factor in the costs of the fuel along with the costs of the boiler. Perhaps you can design a less elaborate boiler system to heat only bedrooms, then use more standard pellet heaters inside the large rooms of the house. To make heat you will spend 3 times as much if you are using diesel, electric, or propane. Wood pellet heat costs 1/3 as uch, so that will be a savings that you will see year after year. Also there really is not that much weight difference, the diesel is heavy and it smells. The propane tanks are heavy too. I will never install a heating system for propane or diesel, and if I buy a house and it has one I plan selling it for whatever I can get for it. Diesel is horrible for the planet and is not going to get any cheaper in the future.

Maybe if you have a floorplan we can see if there is anything that might work. As I said maybe a smaller peller boiler that only heats the bedrooms with radiators. You only need one zone because you can easily turn the individual radiators on and off. If you have a lot of appliances and the hot water heater located in the kitchen then that room already has some heat from those (depending on how cold it gets there in winter). The main living room can be heated by a pellet stove or by some sort of fireplace insert with a recovery system that will increase efficiency. It is also possible to run a fireplace insert with a boiler that will feed radiators in other rooms, however that requires installing radiator water lines in walls with no cavities between wood studs.

I think I am rambling now  Mull over what I said and see if you can come up with any ideas. I wish I still had my pellet fuel vs other fuel costs but I think I tossed it out. But I do remember it was pellets cost 1/3 as much as all the others, so if you diesel heating bill will be $1500 a year then you pellet heating bill would be $400-500 a year. It is a substantial savings and pellets are easy to store and load, Otherwise they make wood burning boilers to heat the house with radiators, and that might even be a little cheaper than the pellets depending on where you get the wood but they are also more work to load, clean, etc. Heck I was looking at a house near a pine forest and if I ended up buying that house I was envisioning a custom pellet stove that would burn pine cones, because the place was lousy with they lying around everywhere. Remember, you already have the house and it is not moveable so you need to design something that works with what you have now.


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## John and Cecil (Dec 22, 2019)

I think your fireplace probably has some sort of heat recovery device. Much of the heat from a fireplace goes up the chimney and a heat recovery device will save some of it. It still will not compete with a metal wood stove inside the room. I hate fireplaces. They look nice but they take up so much space and I would prefer a simple round flue pipe in the ceiling coming down to a pellet stove. I prefer pellets over wood because they do not need to ever be opened while they are running and you do not smell the smoke. If you must stir the wood or reload ir light them, etc then some smoke escapes into the room. The smoke bothers and it makes me cough a lot, however I do not have a problem with pellet stoves. Unlike the fireplace the pellet stove (and wood stove) is all metal and the entire appliance is inside the room, and even the metal flue pipe is inside the room.This means that a majority of the heat you create will be going inside the house and not up the chimney. And they are a simple device so they are not very expensive. I have been searching forever for a mini pellet stove, something that might look like a central vacuum or something mounted on a wall. It would vent through the wall and create just enough heat for a bedroom. But I do not believe anyone makes one yet. They do make oven and stovetop and oven that runs on pellets (for cooking in the kitchen) but I believe it may only be by one or two companies so the price is excessive (no competition).


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## jimclarck (Mar 5, 2020)

The 5 zone is a multi split AC system so will run on electricity. There is no good location for a pellet stove that will be easy to run pipes (I don't like them exposed either) to upstairs bedrooms.


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## John and Cecil (Dec 22, 2019)

jimclarck said:


> The 5 zone is a multi split AC system so will run on electricity. There is no good location for a pellet stove that will be easy to run pipes (I don't like them exposed either) to upstairs bedrooms.


So that helps, a boiler is completely out for heating the upstairs bedrooms with no desire for radiator pipes. I understand completely, I feel the same way. The next question is can you leave the bedroom doors open at night (or do folks need their privacy)? If the doors are in close proximity you might be able to run a pellet stove in the hallway near all the bedroom doors or somewhere near the top of the stairs. Heat rises so it won't want to go downstairs too much unless it must. Perhaps install both an electric heating system in the bedrooms and a pellet stove in the hallway, whatever heat you can provide with the pellets will save you triple as much as the cost of the pellets in electricity. Here is a picture of a pellet stove in a hallway.











The funny thing is thus (actually it is far from funny), if your upstairs bedroom portion of the house is say 50m2 total, and the rest of the house is say another 100m2 total, then it is cheaper to heat the entire house all night with pellets than to just heat the bedrooms with electric. This is why I have been obsessed with searching for a mini pellet heater that mounts to a wall in the bedroom. 

You have a very nice house so ripping out walls and doorways is not in the cards for you. The houses here are terribly designed with small rooms and hallways everywhere. I would prefer a great room with the kitchen dining room and living room all in one giant room, then have a small hallway on the end of the great room with a few bedrooms and bathrooms. Then you run a pellet stove in the living room, another in the hallway near the bedroom and bathroom doors, and supplement the bedrooms and bathrooms with an electric heating system. At the moment this is my ideal setup for efficiency.

That brings me to another invention mostly missing from Portugal, the ceiling fan. A lot of the houses with great rooms have tall cathedral ceilings. When you heat a house the heat rises. so the air up near the ceiling is warmer than the air in the lower half of the room. This is where the reversible ceiling fan comes into play. In winter it spins in one direction and the fan blades push the air from the ceiling down, and in the summer it spins the other way which pushes the air up. They also help to draw air into the windows in the summer. I prefer the whole house fan type system in the summer but the ceiling fan helps in the winter. They are cheap too, in the USA you can get them for maybe $50 (i have purchase small ones on sale for $25) and they only consume about 50-75w of power.


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## John and Cecil (Dec 22, 2019)

Here is my kitchen in my last house. The natural gas forced air heat vent is above the cabinets. In the morning I would turn on the heat and the ceiling air would get warm but the air I was using was not as warm. I would turn the ceiling fan on and it would blow warm air down onto the table area for breakfast.


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