Insulation

[rosinante]

Hi chaps ,
I have loft insulation , also cavity wall insulation , the tops of the walls above windows and corners of outside walls at top are cold enough to cause condensation on wet days esp when humidity is high , Q could I use cavity wall batts to bulk up the insulation under the eaves ? Iwas thinking of 100mm rockwool , the semi ridgid nature I'm hoping would aid installation ,doing it myself , it is a 70s built detached bungalow in Cornwall so damp climate .
Cheers

 

[Kram]

Get a dehumidifier instead &it'll also make the house feel warmer, while offsetting some heating.

 

[gaz1]

cut off 2-3ft of the roll use a stick to push into place

then continue with more roll as you go

another layer smaller say 2ft will give you a stagered layer and give you close to 8" close to the edge of the ceiling

its the closest you will get to bridging the wall to ceiling cold spot

if you have a layer already within your joists then once you have fitted another 2ft towards the edge turn the roll sideways and roll out across the beams

is the best way to do it

 

[Gareth J]

Hi chaps ,
I have loft insulation , also cavity wall insulation , the tops of the walls above windows and corners of outside walls at top are cold enough to cause condensation on wet days esp when humidity is high , Q could I use cavity wall batts to bulk up the insulation under the eaves ? Iwas thinking of 100mm rockwool , the semi ridgid nature I'm hoping would aid installation ,doing it myself , it is a 70s built detached bungalow in Cornwall so damp climate .
Cheers

What sort of cavity wall insulation?

I have blown fluff in a portion of the house. Not had problems with water ingress that many have but I can see with a thermal imaging camera a few places high up where it's missing. Should be able to top up with polystyrene balls.

Either way, yes, insulate the top of the wall. But maybe only the inside leaf of wall needs to be insulated?

Also get a humidity monitor, cheap enough via eBay. It's possible that you have both high humidity inside and a breach in insulation.

Humidity can be reduced with an expensive to run dehumidifier, or expensive to run heating and ventilation. Or cheap to run but expensive to buy MVHR. Even works in Cornwall, I promise.

 

[Matrixx]

The Eves need to be kept clear to aid ventilation, you need air to stop rot in your roof timbers

 

[mtt.tr]

Really no easy fix, out properties are just not designed for insulation.

Though I'm considering a PIV fan

 

[willie.macleod]

The only insulation I'd use for that would be internal wall insulation (plasterboard stuck to insulation sheets), it'll lose a bit of space internally but transform the room. Ideal if you are planning redecorating, if not then a desiccant dehumidifier as @Kram says is the way to go. Don't use a compressor type as they don't work well in colder climates. The desiccant type will add much needed heat efficiently to the room MVHR is great but if the heat isn't there in the first place it can't add any.

The temptation to stick insulation in at the eaves is a recipe for disaster with a cold roof design, unlikely to be able to get the insulation batts into the right place.

 

[Gareth J]

MVHR is great but if the heat isn't there in the first place it can't add any.

A dehumidifier will only add heat at the same cost as any other electrical heater. If expensive electric is your only form of heating, fair enough. But most people burn something cheaper. In a bungalow in Cornwall, that's probably oil or gas, or wood. Or some combination. In which case, economically, you'd more than likely be better off heating with the cheap(er) form and ventilating with mvhr to recover some of the heat.

That's before you consider other benefits. CO2, Particulates, Radon. Though unless the house is very well sealed, they're probably not significant anyway.

 

[gaz1]

The only insulation I'd use for that would be internal wall insulation (plasterboard stuck to insulation sheets),

The temptation to stick insulation in at the eaves is a recipe for disaster with a cold roof design, unlikely to be able to get the insulation batts into the right place.

cold roof design can except insulation over the first part of the wall just not the second if you have extended rafters past the wall it will still insulate and allows the bridging between the wall and ceiling so wont be an issue there

as goes for plasterboard insulation you have 1/2 an hour fire protection and then it becomes an inferno

the modern room is to the right

mixed with plasterbaord insulation on walls and ceiling and you get this

this is what happens when your nails/screws melt

 

[minimutly]

The only insulation I'd use for that would be internal wall insulation (plasterboard stuck to insulation sheets), it'll lose a bit of space internally but transform the room. Ideal if you are planning redecorating, if not then a desiccant dehumidifier as @Kram says is the way to go. Don't use a compressor type as they don't work well in colder climates. The desiccant type will add much needed heat efficiently to the room MVHR is great but if the heat isn't there in the first place it can't add any.

The temptation to stick insulation in at the eaves is a recipe for disaster with a cold roof design, unlikely to be able to get the insulation batts into the right place.

Again I hear this nonsense about compressor dehumidifiers.
How cold will it be in your house this winter @willie.macleod ?
Cold enough to stop the dehumidifier working? The one in my workshop pulls water out right down to 5 degrees or so...
Poor advice sir

 

[addjunkie]

Again I hear this nonsense about compressor dehumidifiers.
How cold will it be in your house this winter @willie.macleod ?
Cold enough to stop the dehumidifier working? The one in my workshop pulls water out right down to 5 degrees or so...
Poor advice sir

While I agree with you a dessicant wheel dehumidifier is far more efficient at maintaining the relative humidity in a house as the moisture is expelled outside, where as a fridge type fills a bucket/ container, needs emptying, and only actually remove the moisture if you empty regularly.

 

[willie.macleod]

A dehumidifier will only add heat at the same cost as any other electrical heater. If expensive electric is your only form of heating, fair enough. But most people burn something cheaper. In a bungalow in Cornwall, that's probably oil or gas, or wood. Or some combination. In which case, economically, you'd more than likely be better off heating with the cheap(er) form and ventilating with mvhr to recover some of the heat.

I agree if you have a cheaper form of heating then that should be used to heat the internal surfaces above dew point.

However, if you don't or can't do that then a dessicant dehumidifier provides a very controllable method of background heat and moves the air as well as drying it. All three combined do away with the damp problems.

Turn on the 30kW oil boiler and your rads pump heat into the rooms but not at a constant low rate and not for very long which is why the walls are staying cold. Radiator heat isn't great at moving between rooms in the same way a 500W dehumidifier can pull moist air out of a whole house if the doors are left open. Its efficiency is that the electricity is not only heating but removing the presumed excess moisture as well moving the air constantly.

I have mvhr in my house, fine in a new build but retro fitting would be the last thing I would do in an old bungalow with little insulation. For the last 10 years I have recommended around half a dozen people to get dessicant dehumidifiers who also have oil boilers, so far no one regretted the investment.

 

[willie.macleod]

Again I hear this nonsense about compressor dehumidifiers.
How cold will it be in your house this winter @willie.macleod ?
Cold enough to stop the dehumidifier working? The one in my workshop pulls water out right down to 5 degrees or so...
Poor advice sir

Of course a compressor dehumidifier works above freezing. What ot won't do is pull out the same volume of water as a dessicant type.

I speak from experience, I built my own house and lived in a caravan for years while doing so. I live in a cold wet windy location and have had my share of living in mouldy houses.

 

[willie.macleod]

While I agree with you a dessicant wheel dehumidifier is far more efficient at maintaining the relative humidity in a house as the moisture is expelled outside, where as a fridge type fills a bucket/ container, needs emptying, and only actually remove the moisture if you empty regularly.

Haven't seen any decent dehumidifier yet that can't be plumbed into a permanent drain. Nothing to do with type.

 

[willie.macleod]

as goes for plasterboard insulation you have 1/2 an hour fire protection and then it becomes

Not sure about this nonsense. I built a concrete house but by your thinking I assume you think all timber frames are death traps? How do you think my insulation is going to catch fire sandwiched between a concrete core and a sheet of plasterboard with no air gap? You need oxygen as well as fuel and heat. Plus try to get modern insulation to catch fire. Not easy. If you are still in the house half an hour after a fire starts that's another problem, where are you fire alarms?

 

[addjunkie]

Haven't seen any decent dehumidifier yet that can't be plumbed into a permanent drain. Nothing to do with type.

Thats the thing with a dessicant wheel type the regen is simply blowin* dry air back through a segment of the wheel and venting* outside. Common on large building management systems.

Desiccant Dehumidification Technology - Munters

Munters dehumidification systems remove moisture from the air by using a desiccant; a material which attracts and holds water vapor. Contact us to learn more!

www.munters.com

 

[gaz1]

Not sure about this nonsense. I built a concrete house but by your thinking I assume you think all timber frames are death traps? How do you think my insulation is going to catch fire sandwiched between a concrete core and a sheet of plasterboard with no air gap? You need oxygen as well as fuel and heat. Plus try to get modern insulation to catch fire. Not easy. If you are still in the house half an hour after a fire starts that's another problem, where are you fire alarms?

really thats what grenfell fire thought and it burnt down and people are installing it in there houses with no warnings of the dangers of the stuff

as goes for council they dont care its what you use for insulation its your problem not theres, they dont even give you an advisary warning you of the insulation is a fire risk and they know full well it is

it may say fire proof but its not it will burn and at temps of 1500+ it will catch fire and melt metal screws holding it on walls and onto ceilings i fit the stuff and no one warns customers of the dangers

like i said you have 1/2 an hour fire rated gear with plasterboard after that its through and burning away mix in flash over temps at 1500-2000f and its a total game changer and you have less time

 

[Gareth J]

I have mvhr in my house, fine in a new build but retro fitting would be the last thing I would do in an old bungalow with little insulation. For the last 10 years I have recommended around half a dozen people to get dessicant dehumidifiers who also have oil boilers, so far no one regretted the investment.

Conversely, a friend of mine, who lives in a relatively poorly insulated bungalow in Cornwall recommended the unit I bought to me, as he has the same. He has no regrets and neither do I. His draws air from above a woodburner and the bathroom and inlets into the two bedrooms. I dry all washing inside with no condensation, for the cost of running a 30W fan.

 

[DAPPH]

Get a dehumidifier instead &it'll also make the house feel warmer, while offsetting some heating.

It costs far more to heat moist air than dry air as you have to heat every one of those microscopic droplets of water in the moist air to the same temperature that you require the room to be.

Even running a small dehumidifier 24/7 like I do it's only drawing the max rated wattage of 330 watts for the short period it is used to heat the thing up to de-ice the coolant radiator. The rest of the time it's just a 9 watt or so fan drawing moist air across the coolant radiator till it's iced up again. Then once the humidity reaches the preset humidity level of 50% humidity (in our case) it goes into sensing mode and stops the fan as well.

Something else I've done to reduce humidity in the bungalow is install two-wet room extractor fans that come on with the bathroom's LED lights and they are on an adjustable timer so stay on for forty minutes after the wet room lights are switched off. In the other moisture rich area, I have an over the hob to the outside extractor with self-closing louvres on the outer end to stop back draughts and rain coming in. We rarely use hot tap water in the kitchen sink, a big dishwasher usually does a days' worth of pots & pans etc. overnight on off peak electricity in the sealed dishwasher. Which runs on cold fill, so it only heats the water to the temperature needed for washing, it's not only saving money it also keeps the humidity lower than if it was hot filled & needed cold water to cool it to the right temperatures for dishwashing.

No longer do we have a letter box that allows cold draughts to pass through it, the front door doesn't have one. Instead, we have an external bespoke made marine grade stainless steel, floor vented, hinged, lidded box some 10" x 16" x 16 " deep fixed to the wall outside the door, it's stuck on the wall with big Rawl Nuts, 10 mm stainless studding and half a dozen break off domed security nuts.

Almost all pan cooking in the kitchen is done with pan lids in place and nothing much ever gets viciously boiled because such boiling piles the moisture into the air.
Even if the hob extractor is going full chat some moisture will still escape from the cooker hood over the hob, not much, but it's noticeable when we see a little bit of slight misty condensation high up on the tripple glazed kitchen window on a frosty day at evening meal cooking time.

Strange as it may seem, both Alison and my daughter used to have waist long hair which took ages to dry, after noticing black mould appearing in their bedrooms before the alterations and improvements were done to the bungalow they both said they were going to have a much easier to care for, shorter hairstyle that could be quickly towel dried ... that made a considerable difference to humidity levels on the indoor humidity & temperature monitor. Humidity used to be up above 70% even with all the ill-fitting doors, windows and the breezy letter box pre modernisation being done.

One last thing that is also surprising is the amount of water you put on towels and leave them to air dry in the bathroom. Years ago, whilst in HMF back in the 70's in one particular unit I was attached to, on most weekday morning we used to do battle runs packing a fair bit of kit.
After an hour and a half of grueling running we'd be back at our barracks, we'd use communal showers and tried and get dried on our tiny 3x 2 foot issued green terry towel towels. Which usually resulted in most of us still being overly damp to start the days normal work.

A concerning outbreak of Athletes Foot, spotty black mouldy armpits & nether regions occurred in a lot of people as a result of not being able to get sufficiently dried when needed. Numerous cans of special foot powder & a tube or two of antifungal cream cleared most guys up PDQ.
The medical officer overseeing the medical problem ordered that we got issued with three more of these issued hand towels.... . more kit to carry.

One lad had the bright idea of using a much smaller thick cotton dish cloth that he'd dyed green to take off most of the water first wring it out as needed, then use an issued towel to get properly dry.

For field craft reasons we weren't allowed anything other than the issued green stuff , anything issued in white had to be handed in and exchanged for camo or green colours etc. It worked a treat and ever since I've nearly always used a pre drying cloth to remove the majority of shower or bath water before using the bath towel to finish up

Doing a home science & math's project in the summer holidays when my son was 12 (1992) we decided to measure just how much water we were removing by doing the pre dry using the new on the market Miracle Fibre Cloth's that were supposed to hold far more water than other cloths.
The difference between weighing the wet and dry was amazing, we weighed just under half a pint ( 10 fluid ounces ) between us which was saved from going on bath towels & being allowed to evaporate into the upstairs rooms . God only knows how much moisture my two long haired females put in the air upstairs after showering and electric hair drying their long-wet hair.

 

[knighty]

I've used dehumidifiers a fair bit, at home drying cloths and at work keeping anything from damp rooms dry to areas where we store dry treats etc. (have a walk in dehydrating machine)

factory is steam cleaned daily, lots of drums of water tipped over during the day etc. etc. so very moist area

for me, the compressor units have always worked better than the desiccant type, I haven't caught the drain off water (all plumbed in) for figures to back that up, but I've had areas not kept dry enough with the desiccant type which were/are kept dry the the compressor type

only dried the desiccant type after reading so much about them being better in cold weather... It must have to be bloody cold to make a difference

plus desiccant type use what... five times the power of a compressor one?