Optimum size for new home

[kenneal - lagger]

I live in a victorian house with gappy windows. There is often a window open, but I may shut it on Thursday.

When it is blowing a freezing gale outside there is nothing you can do to keep any heat that you have generated inside the house. In these conditions, unless you have an enormously oversized heating installation, there is not a lot that you can do to keep the house remotely comfortable. Even if you could raise the temperature to a reasonable level the air movement would still make the house uncomfortable.

If the house is airtight you can always open a window. If the house leaks like a sieve shutting a window when it gets too cold and breezy will not make much of a difference. Not many people want to live in an ice box during the winter and it can be positively unhealthy to do so for some people: children and the old for instance. Warming a house and then letting that heat go is not good for the environment either but if you don't believe in global warming then I suppose the environment can go stuff itself.

Whether one sort of bacteria or mould grows or another will depend on the temperature and the humidity and this can be controlled by varying the heating temperature and ventilation rate controls. It just requires a bit of thought and education. If everyone adopted the attitude of "I like the cold so everyone else should" we would still all be living in 1700s houses with all the deaths from hypothermia that went with them.

[woodburner]

I live in a victorian house with gappy windows. There is often a window open, but I may shut it on Thursday.

When it is blowing a freezing gale outside there is nothing you can do to keep any heat that you have generated inside the house. In these conditions, unless you have an enormously oversized heating installation, there is not a lot that you can do to keep the house remotely comfortable. Even if you could raise the temperature to a reasonable level the air movement would still make the house uncomfortable.

That's one opinion I suppose.

If the house is airtight you can always open a window.

Could do, but most people don't

If the house leaks like a sieve shutting a window when it gets too cold and breezy will not make much of a difference. Not many people want to live in an ice box during the winter and it can be positively unhealthy to do so for some people: children and the old for instance. Warming a house and then letting that heat go is not good for the environment either but if you don't believe in global warming then I suppose the environment can go stuff itself.

You make a lot of assumptions.

Whether one sort of bacteria or mould grows or another will depend on the temperature and the humidity and this can be controlled by varying the heating temperature and ventilation rate controls. It just requires a bit of thought and education. If everyone adopted the attitude of "I like the cold so everyone else should" we would still all be living in 1700s houses with all the deaths from hypothermia that went with them.

Problem is, from the NS report, it doesn't work, so you get bad bugs.

You might also find a high level of poverty and low level of medical treatment contributed as well. There are plenty of countries today, notably in Africa. Not cold enough for hypothermia, but plenty of people die

[kenneal - lagger]

Some people are blind because they don't want to see.

So rather than educate people we should build cold homes or move them all to Africa where it's warmer.!

[woodburner]

Some people are blind because they don't want to see.

So rather than educate people we should build cold homes or move them all to Africa where it's warmer.!

With a radiant heater, eg wood stove, you don't need high air temperatures. Farm shops use this for their till operators in the form of an infrared lamp.

[kenneal - lagger]

Try and stop a wood burning stove convecting most of it's heat. You're grasping at straw now!

[kenneal - lagger]

I happen to know a bit about building, building physics and thermal comfort. I've had experience of well insulated and airtight homes and I've had experience of draughty homes and I know which one I and most of the population will chose. I know how to ventilate a home but many people just need to learn.

[woodburner]

You think we should design for better microbial ecosystems. What would a healthy building look like? Are we depending too much on mechanical ventilation and not spending enough time with windows open?

I want to be cautious because that’s a new area. We’ve conducted one study in a hospital environment. The study demonstrated that in this one environment in Portland, a very green place, if you open windows in outpatient rooms, you get microbes in those rooms commonly found on plant leaves and in the soil. If you close the windows and run the mechanical ventilation system, in the air you tend to have more microbes commonly found on the human skin and in the human mouth. If you look at how evolutionarily related DNA sequences from the air and bacteria are to known pathogens, the proportion of sequences more closely related to pathogens is greater when you have the windows closed and the mechanical ventilation system on. But this is just one study in Portland. If you’re in a more polluted city, we don’t know the tradeoffs between running a mechanical ventilation system versus keeping the windows opened.

Right now, building code is centered on this concept of keeping the outdoors out. It’s not possible to keep microbes outdoors. Microbes are going to colonize spaces. If you’re not letting outdoor microbes inside, then the indoors is going to be colonized by people. Those microbes are going to be reproducing and populating the space. The concept of keeping microbes out is outdated. The new way of thinking is: We know there are going to be microbes colonizing the indoor environment, unless you’re in a controlled environment like an operating room. If the indoor environment is going to be colonized by microbes, what kind of microbes do we want to be colonized with? Designers are going to start thinking about using this ecological framework versus trying to keep the outdoors out.

I suspect Jessica Green may have been conneced with the NS article. No doubt Biff can comment.

more.......

[Tarrel]

I think maybe the debate here is around two extremes. You can have a property with natural trickle ventilation through, say, traditional sash windows that doesn't result in a "howling gale".

I've lived in hermetically sealed, well-insulated boxes and more traditional, older houses that are not especially thermally efficient. I have to say I prefer the latter. I feel better and breathe more easily.

Our approach to efficiency is to use the Rayburn and multi-task with it. It runs pretty much 24/7 in winter, keeping the house at a comfortable temperature by compensating for the thermal losses. But it also takes the place of an electric cooker, electric kettle, tumble dryer, etc. and provides hot water.

Having said that, we have been working on plugging some of the more obvious gaps in our property!

[ujoni08]

This is a topic that I'm always thinking about during the Winter months. Incidentally, can anyone say what sort of relative humidity is best to aim for in a house?

[adam2]

Between 40% and 60% RH is normaly considered optimum.

[ujoni08]

Thanks, Adam2. That's what I generally achieve, with a combination of ventilation and de-humidification, though on some rainy days it peaks briefly at around 74% inside the house. That's without any heating on. I haven't used any heating so far this Autumn, so I'll see what effect that has.

I've just had a chimney liner and pot fitted, and given the old Morso a polish, so I'm feeling quite chuffed.

[PS_RalphW]

Since (parts of) my house were built in the 1700s I am pondering what I can do to reduce drafts.

Actually, the house has been rebuilt and repaired to the extent that the older parts seem reasonably draft-proof, although I am sure secondary glazing would improve matters. It is the newer bits that really let it down. The shower room has an extractor fan linked to the light which in practical terms is a 6 inch circular hole straight through the wall. You can see straight through to daylight. Two of the exterior doors are single glazed and have 2mm plywood panels. One of them had an unfilled 5mm gap and a catflap which blew open in the lightest breeze.

I do not and could not draft proof to passive house standards, with two log burners running I would quickly run short of oxygen. When operating correctly, (the better one) should burn the wood at 70+% efficiency and pull in only enough air to sustain combustion.

The oil burner is about 25 years old, and replacement seems a priority, once I have got the insulation up to the point where a smaller unit could meet the demand.

[RenewableCandy]

Single-unit MHVRs don't have that bacteria problem that the NS article was talking about, and it's not too difficult or costly to fit one in that 6" hole. We had one in our old bathroom and it was nice to smell garden scents while standing in the shower in a warm room. Highly recommend those things for the bathroom!

[woodburner]

Mmmm, if we had one we'd forever be getting the aroma of horse urine from all the plonkers who smoulder their stable shovellings.

[adam2]

Thanks, Adam2. That's what I generally achieve, with a combination of ventilation and de-humidification, though on some rainy days it peaks briefly at around 74% inside the house. That's without any heating on. I haven't used any heating so far this Autumn, so I'll see what effect that has.

I've just had a chimney liner and pot fitted, and given the old Morso a polish, so I'm feeling quite chuffed.

74% is a bit high if reached regularly and could lead to mould or damp if long continued, but for brief peaks I would not worry.

If the RH in your home is a bit high, but it is not cold enough to justify heating, then use of an electric dehumidifier can be very helpful at modest energy cost.
If an off peak tarrif is available then that makes it even better.