Rational Questions about Dumb/Normal Houses

I’m really into learning about this topic! But… I have a normal house in suburban Maryland. Stick frame, basement plus two floors, gas furnace with forced air, etc. I can’t tell how I could ever use a RMH in this building. Can I ask some dumb questions?

1. You can’t just install this on the hardwood floor in the living room, I assume. Can it go on the concrete basement floor?

2. How does the heat get upstairs?

3. If the house has no chimney and never had a wood-burning anything, where do you put one?

4. Is this kind of retrofit even a good idea?

Hi David;
There are a whole lot of folks out there in the same situation as you are.
Adding a wood burner in a suburban home that has never had one, is a big step.
Some towns may not allow wood burning at all.

I'll try to answer your questions.
1)  Yes, you can build over your hardwood floor, as long as there is adequate support below for the extra weight.
Clay bricks are laid flat with air gaps. A double sheet of cement board is placed on top and your brick bell or bench is built elevated on that.
2) Registers thru the floor.
3)That is a big question.  It depends on the home and its construction.  
Ideally, a block chimney built on an end wall would be a high-end choice.
Next would be to have a class A roof jack installed just below the peak and an 8" insulated stove pipe up thru the roof.
The last choice is to, exit the house horizontally thru the wall. Then use insulated stove pipe up and over the peak.
4) Big smile here on that question... I might be a bit biased about this.
I believe that its the best idea in years.

David,

1. For masonry heater that can weigh 3000 lbs and easily more you need a solid foundation, at least 8" thick with #4 rebars 8" on center (two grids, on top and bottom of the slab). If I had to build a heater in such a setup I would first pour a thick slab in the basement then I would build a shaft wall 3'x3' (or bigger) from concrete blocks and would pour a slab on top of that and start building the heater there. Another, probably cheaper, but not necessarily easier option would be to install steel H-beams on the top of the concrete basement walls diagonally in the corner of the walls and pour slab on them with right amount of reinforcing.. I saw the latter solution used in some build in Europe.

2. I saw a build in Spain that was using one heater to provide heat to three levels of the house, There were also such solutions used in Russia. It will definitely complicate the design a lot and no matter what design, the basement would be heated and I think this is not your goal. It would be better to have a heater on the room level.

3. You will need a chimney. If you don't care about aesthetics, a double wall stainless chimney can be used. It should be as straight as possible, without unnecessary bends (each bend increases the drag of fumes)  and should be tall enough, 16' would be probably sufficient. It can go through all the floors or be located outside, but it's always better to have the chimney inside of the building envelope, because it will be warmer at the start and will also radiate back any heat (low in case of properly designed heater) back to the house.

4. It's a project that can be done, but the lack of solid platform at the room level and the lack of chimney will make more challenges.  If you want to have it you should do it yourself, otherwise it may cost a small fortune.

Personally, I would rephrase your thread title: "Rational Questions about Dumb/Normal Houses."

Your questions are not dumb; they are smart. I currently live in a house much like yours, stick build and designed to be dependent on cheap natural gas from the grid. Not my preference, but the currents of life brought me here.

I understand the questions you are asking, and currently struggle with them myself. It's a substantial undertaking in a main dwelling. Less so in a greenhouse.

May I ask:
- What is your climate?
- Urban or rural?
- Is your municipality laissez-faire or heavy on permits?
- Are you willing to negotiate firmly with your insurance provider?
- Do you have ready sources of wood?
- Are you in this property for the long term? I.e., is it worth your investment of time and effort and dollars?

Haha I love it, that title would have been better.

Good counter questions, and even if the answer to some is ‘no’ it’s worth it to me to learn. It’s Maryland so a fairly mild climate. Suburban neighborhood with probably average permitting requirements. I wouldn’t know where to begin negotiating with insurance, I’ve never done that. But stay long-term or go, it would be useful to know what this retrofit would take if we move and want to analyze doing it in a new house with similar conditions.

David, you might find the answer to your dumb question about normal house here:

The FAQ thread might be a good place to start:

https://permies.com/t/191801/Building-Ultimate-Rocket-Mass-Heater

You can't build one in a conventional home.

There are RMH systems suitable for any and all weight limitations and building systems.

You can't build one in a city.

Not only are codes coming around, but there are also now multiple UL-certified Rocket Stoves on the market that can be purchased and delivered, ready-to-install.

You can't build one in a rental.

The Liberator and the Pebble Style RMH are just two examples of RMH systems that are easy to install AND uninstall, should the need ever arise.

Douglas nailed the questions to ask yourself. Especially do you have a source of wood? I would add what is your goals with a rmh? I know if I had a conventional built house I would first look at a pellet stove and a backup source of electricity to run it. An imperfect solution but much easier to implement.

David McDonough wrote:......

1. You can’t just install this on the hardwood floor in the living room, I assume. Can it go on the concrete basement floor?

2. How does the heat get upstairs?

3. If the house has no chimney and never had a wood-burning anything, where do you put one?

4. Is this kind of retrofit even a good idea?

I'm going to offer some dumb answers/comments as I have no where near the experience and insights on RMHs as do the other respondants....I use a rocket heater in a shop space mostly for educating myself about their operation, but it has no mass and therefore relatively little weight and heat retention.

With reference to #1, I understand the "let's be as safe as possible" argument concerning the weight of a RMH on a hardwood floor, but with the manner in which that weight is distributed, is it really that much of an issue?  Are there examples where this was not heeded ...... and with disastrous consequences?

For #2 as someone noted elsewhere, if by chance the house is ducted for forced air heat, there may (in addition to heat registers) be a way to use/retrofit a furnace fan to circulate the heat from the basement to the rest of the house.  We commonly did this when I grew up in the US Midwest in the summer months to pull cooled air from the basement to the upstairs of the house.

From experience, #3 (depending on codes) might be even easier with a RMH than with a conventional wood stove.  We were not allowed to use the old brick chimney for our wood stove and so ported the stove out the main wall of the house.  From the outside of the house, this is about 10 ft above ground level.  The copious sections of class A chimney then ran up through the roof soffit and at least another 15 ft before ending with a cap ($$$).  A similar retrofit for a RMH I suspect might be done at a lower height outside of the home and then possibly require less class A chimney to produce the required draft,.....but this latter part may be beholden more to code and wind currents in your area.

#4)  That more depends on the homeowner and how they perceive the cost/benefit of the RMH for their own lifestyle vs. potential re-sale issues with the install.

One note:  We live in a cold dry winter region now.....woodstove heat is 'drying' and just dries the house out more.  My wife ran wood stoves in western Oregon in the winter where the drying of the stove heat was WELCOMED!  Would Maryland be classified as a more damp cold winter?  RMH heat might be perfect for that situation.

David Baillie wrote: Douglas nailed the questions to ask yourself. Especially do you have a source of wood? I would add what is your goals with a rmh? I know if I had a conventional built house I would first look at a pellet stove and a backup source of electricity to run it. An imperfect solution but much easier to implement.

Good questions for someone wanting an RMH.

This might help them choose between a stove and an RMH:

a massive stack of firewood for a conventional wood stove

a teeny-tiny, neatly stacked half-cord of kindling, and/or a pallet of waste paper, representing the fuel required to operate a RMH for 1 cold winter

Which would you choose, folks?

From the FAQ above link.

Anne Miller wrote:

David Baillie wrote: Douglas nailed the questions to ask yourself. Especially do you have a source of wood? I would add what is your goals with a rmh? I know if I had a conventional built house I would first look at a pellet stove and a backup source of electricity to run it. An imperfect solution but much easier to implement.

Good questions for someone wanting an RMH.

This might help them choose between a stove and an RMH:

a massive stack of firewood for a conventional wood stove

a teeny-tiny, neatly stacked half-cord of kindling, and/or a pallet of waste paper, representing the fuel required to operate a RMH for 1 cold winter

Which would you choose, folks?

From the FAQ above link.

Anne, I would amend my post above to add that its mostly the heavy mass modifications that I would be hesitant to suggest  on an already built house. As Thomas pointed out that there are many lighter ul approved portable solutions out there. I do find that not enough is mentioned about the mass already in your house namely the 2-5 tonnes of gypsum , concrete slab, ceramic tile etc being warmed up by the house. I think the pellet stove is an option for those without a source of wood already as an easy modification to an already existing house. Personally if I was building a slab on grade low energy home I would go the RMH or masonry heater route.
Cheers,  David

David said, "I do find that not enough is mentioned about the mass already in your house namely the 2-5 tonnes of gypsum , concrete slab, ceramic tile etc being warmed up by the house.

This too is something worth mentioning and I too have not seen much mentioned.

This is the first house we have lived in with a concrete slab.

It is amazing how much heat it will mass.  Some of my rooms will stay at 60 degrees inside without heat even when it is 5 degrees outside..

Anne Miller wrote:

David said, "I do find that not enough is mentioned about the mass already in your house namely the 2-5 tonnes of gypsum , concrete slab, ceramic tile etc being warmed up by the house.

This too is something worth mentioning and I too have not seen much mentioned.

This is the first house we have lived in with a concrete slab.

It is amazing how much heat it will mass.  Some of my rooms will stay at 60 degrees inside without heat even when it is 5 degrees outside..

So I decided to crunch some of those numbers...
We installed 10000 sq ft of drywall. We used the ultralite so that's 1.22lbs/sqft so 12200 lbs or 5.5 tonnes of mass in the walls and ceiling.

Actually this is a sub-topic I had not considered....the "slab-on-grade" as an integral part of heating (and cooling?) design for homes.  Certainly I'm aware of the in-floor heating with embedded pipes that circulate warm water, but it seems an 'unsold' concept that by designing the floor plan properly with a concrete slab, the slab could become a heat battery and release heat when the primary heat source (RMH or otherwise) is not operating.  Our old farmhouse we currently live in has 1.5 - 2 cm thick plaster on lathe.  Although poorly insulated behind that lathe, the plaster itself likely can hold a fair amount of heat once brought to temperature.

In floor heating has been in use for a long time, in the UK and France at least heating the concrete floor mass is a pretty standard method for any new home over the last 20 years or so.
The method requires laying down 4-6” foam insulation then a electric heat mat is laid on top of the foam and the 4” cast concrete poured on top of that.
The heat mat is a low wattage and very economical to run, in my particular district all new houses have very strict regulations about insulating new houses, basically all you need are a few candles to warm up one of these modern constructions!

Here in floor tubing would be the norm. I've seen electric but not often and usually under tile. The cost of setting up the zones and laying the tubing was not expensive. Again about 10 tonnes of mass in the basement slab. You do need to insulate well otherwise you end up with it as a heat drain.

John Weiland wrote:   Our old farmhouse we currently live in has 1.5 - 2 cm thick plaster on lathe.  Although poorly insulated behind that lathe, the plaster itself likely can hold a fair amount of heat once brought to temperature.

Not to be contradictory, but if we consider thermodynamics of heat, we can consider how heat travels from warmer to colder in the winter time and summer time. HOT outside, wanting to get into cooler inside, or equaling of temp.  Yes, it can take longer to get the plaster warmer both winter and summer, but from there on- thermodynamics takes over.

So with the statement that "1.5 to 2 cm of plaster getting warm, and staying warm", --- with poor insulation beyond the lathe, simply said, this does not happen, because of thermodynamics, The direction of heat transfer is --the warm will be going to cold, vs warm plaster to warm home inside,  with poor insulation, it is going to keep going. OUT not back into the room. Thermal blocking, unless there are other unknown physic's I am not aware of, it about the only way I know to keep this from happening.  

To look at this in a very simple way, 4 cm of plaster will gather/consume/store double the amount of BTU's that 2 cm's will, but with poor insulated ways beyond the lathe, it will not retain it any better.

Scott Weinberg wrote:

John Weiland wrote:   Our old farmhouse we currently live in has 1.5 - 2 cm thick plaster on lathe.  Although poorly insulated behind that lathe, the plaster itself likely can hold a fair amount of heat once brought to temperature.

Not to be contradictory, but if we consider thermodynamics of heat, we can consider how heat travels from warmer to colder in the winter time and summer time. HOT outside, wanting to get into cooler inside, or equaling of temp.  Yes, it can take longer to get the plaster warmer both winter and summer, but from there on- thermodynamics takes over.

So with the statement that "1.5 to 2 cm of plaster getting warm, and staying warm", --- with poor insulation beyond the lathe, simply said, this does not happen, because of thermodynamics, The direction of heat transfer is --the warm will be going to cold, vs warm plaster to warm home inside,  with poor insulation, it is going to keep going. OUT not back into the room. Thermal blocking, unless there are other unknown physic's I am not aware of, it about the only way I know to keep this from happening.  

To look at this in a very simple way, 4 cm of plaster will gather/consume/store double the amount of BTU's that 2 cm's will, but with poor insulated ways beyond the lathe, it will not retain it any better.

So absolutely critical to make this point. Mass without insulation from the cold contributes very little.

Yes, .... agreed.  The poor insulation in an otherwise well-constructed house is only equaled by my anemic ability to construct sentences and arguments. ;-)  My inclusion of "poorly insulated" was meant to convey (again, poorly) the somewhat futile nature of heating that plaster since, in itself, it has heat retention value, but no insulating value.  Thus, points well taken.....just as it is heating up on the warm side of the plaster, it is equally dissipating to the universe at large on the cold (poorly insulated) side of the plaster.  Over this winter, with just minutes ago another $280 paid to the propane delivery service, I've been mulling over the various summer insulation projects to be prioritized, and trying to figure out the vulnerable spots in the home.  Fox James' comment (from the UK?) that "in my particular district all new houses have very strict regulations about insulating new houses...." is a sentiment I'm pretty sure does not exist in the US that I know of and can imagine developers screaming about being over-burdened if such were to be the case.

John, I live on an island between France and England, I have worked in the building industry all my life.

Standard requirement for all new habitual buildings requires … cavity external walls with 4” solid foam in the cavity and 1.5” foam backed plasterboard on all internal walls, roofs require a minimum of 5” hard foam plus insulated plasterboard but, very often 7-8” is used.

All new builds are pressure tested, meaning it is impossible to slam an internal door!
The building inspectors are present throughout the build and are very strict on enforcing regulations.

You can still have wood burning stove but again they must be of a modern design, most have vermiculite insulated sides and regulated air flow ie you cant restrict the fire right down low!
 Also you must use a twin wall insulated chimney.

Even old building restorations must comply with up to date insulation requirements unless they are listed as a historical interest.
My own house is stone built in 1887  and was revamped in the 1990s so not so well insulated but we had to replace our open fire places with box stoves and insulated chimneys a few years ago.

However, I still have two rocket stoves on my property, just not inside the main house.

Ontario has similar very tight building requirements as well. It can be a burden but lowers Costs over the lifetime.

For the folks in the mainland US, here is a deal to get the Liberator with free shipping, details here:

https://permies.com/t/208528/Free-Shipping-Liberator-Rocket-Heater

I have no experience to add here, but if the home is heated with an older natural gas furnace (i.e. not high efficiency), the house has a chimney already.  Is there any way to tie into that?  My understanding is just enough to be dangerous, so I get that we need to be able to ensure there are no leaks and things are set up properly so gases exhaust rather than create a backdraft.

@Fox, do you know what sort of R-value those standard would equate to?  I do know of a local house (smack dab near the middle of Canada) that was retrofitted to have R60 walls and R100 roof.  From a heating perspective, the furnace doesn't need to kick in until about -20 C and there's no need for air conditioning in summer.

Hi Derek, we use a different letter to define values but apparently I am not allowed to use that letter on this forum ha ha

Fox James wrote:Hi Derek, we use a different letter to define values but apparently I am not allowed to use that letter on this forum ha ha

That's funny and sad all at the same time.  

Thanks...I trained in engineering, so the description of the units makes some sense to me (electrical / electronics and computer science for me, so I don't pretend to get it all, but get the basics of thermodynamics).

Fox James wrote:Hi Derek, we use a different letter to define values but apparently I am not allowed to use that letter on this forum ha ha

That is very odd... I know I've used the" R "value abbreviation before and the "U "one... Both are units of measurement not short hand...
Aha! It flagged me as well. I put them in brackets and it worked. That is a system flaw though.

Haha, don't sweat it. It's just bots trying to ensure communication involves, you know, actual words. Which are better at conveying actual concepts. Which I personally think is generally more helpful.

Otherwise it's Sk8er Boi and other assorted doodles. Ugh.

Here Paul talks about having his RMH in the FPH living room