The hot tub that feels like a stage

Buy nothing yetMove the table before you buy the pergola.

Before you buy a pergola, move the table.

Every change below is put into the plan and the whole model is run again. That is why a pergola's winter cost shows up here without anybody having written it down, and why the cheapest thing that actually buys hours back is allowed to win.

Fixing

For

Reading at

7:00 PM·October

The sun is down.

Where it stands now

In the hot tub after dark

In the tub does not work for the hot tub after dark right now, and light after dark is why.

“No” means the model does not support this use under the conditions being read. The controlling limits are listed below.

Past the limit Light after dark is about 92 / 100 — 57 over (at most 35)Estimate: Worked out, but at least one input was assumed rather than measured.
At this hour the seat is much brighter than the ground the observer is standing on, which is what makes a person read clearly from outside.
Any lamp near the water makes the tub the brightest object in the garden and everything beyond it invisible.
Close to the limit Privacy exposure is 48 / 100 — 18 over (at most 30)Worked out: Computed from the geometry, the sun and the weather you gave it.
Something already interrupts part of the line, but not all of it.
People are least clothed and most lit at the same moment, which is why this fails on sightline far more often than on temperature.

What would change this. This would change if light after dark were measured and came out differently. The figure is an estimate, not a tape.

Confidence low (49%). Treat this as a starting hypothesis, not an answer.

What this answer was built from

Use: In the hot tub after dark
Place: In the tub
Weather: Cold continental, short intense summer, long hard winter (scenario shape), scenario (from a published source)
Method: Traced geometry and radiation at this hour, measured against what this use needs

The smallest thing that buys hours back

A second seat 19 ft 8 in south

A second seat 19 ft 8 in south moves this from No to Tight without solving any single limit outright.

Summer solstice, 21 June: 3 hours usable now, 1 hour with this change. 2 hours given up.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

+4 hours this daymove it

Ranked by hours bought on this day, then by the least effort. Within half an hour, the change that gives up less winter sun comes first — not the biggest score at this clock time.

Not offered, and why

Glare is not what is limiting this seat, so turning it changes very little.
Wind is not the limiting factor at this spot, so a windbreak solves a problem you do not have.
Nothing overhead here to hang a curtain from yet.
Nothing here has usable space underneath it.
The sun is not up at this hour, so there is nothing to stand in front of.
There is no sun to shade at this hour.
No mature canopy here to work on.
This observer is looking down, and depth does nothing against a downward angle.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
Nothing here is relying on a deciduous canopy, so there is no winter gap to fill.
This point is a place for people, not a place for a plant.
This ground already sheds water quickly.
This surface already drains freely.

23 changes, tested at 7:00 PM in October

One at a time, so you can tell what caused whatLook at the plan

Does it have to suit you?

All 23 changes, in the order the engine ranked them. Say something about your situation and the ones that would not suit you get set aside.

I rent, so nothing permanentRules out anything that cannot be taken away again.
Nothing that needs a builderRules out changes that need footings, trades or a structure fixing to the house.
I want it working this seasonRules out planting and anything else that only works once it has grown.
I will not maintain itRules out anything needing regular watering, pruning or seasonal putting away.

TestAn afternoonYou can undo it

A 9 ft 10 in umbrella

ForecastWorksfrom No

A 9 ft 10 in umbrella fixes light after dark and privacy exposure.

A 9 feet 10 inches canopy at about 7 feet 7 inches, set square over the table.

Gained: Light after dark
Privacy exposure
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: A 9 ft 10 in umbrella
If it worked: light after dark and privacy exposure no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 7 feet 7 inches and about four inches either way changes whether it works.

+4 hours of usable time on this day. Opens 7:00 PM to 11:00 PM.

Summer solstice, 21 June: 3 hours usable now, 4 hours with this change. 1 hour gained.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

It does not meaningfully change the beam in either season.

TestAn afternoonYou can undo it

Remove The floodlight and mark the route instead

ForecastWorksfrom No

Remove The floodlight and mark the route instead fixes light after dark and privacy exposure.

Take out The floodlight and put low shielded markers along the route in from the house. Being the brightest thing in a dark garden is the same as being on a stage, and the light that makes the step safe does not have to be the light you sit in.

Gained: Light after dark
Privacy exposure
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: Remove The floodlight and mark the route instead
If it worked: light after dark and privacy exposure no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Try it on the plan, then go outside and see.

+4 hours of usable time on this day. Opens 7:00 PM to 11:00 PM.

Summer solstice, 21 June: 3 hours usable now, 4 hours with this change. 1 hour gained.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

It does not meaningfully change the beam in either season.

TestA projectYou can undo it

A 7 ft 10 in screen 9 ft 7 in from the seat

ForecastWorksfrom No

A 7 ft 10 in screen 9 ft 7 in from the seat fixes light after dark and privacy exposure.

A screen 7 feet 10 inches high and about 9 feet 1 inch wide, standing 9 feet 7 inches from the seat on the line to Right neighbour's bedroom.

Gained: Light after dark
Privacy exposure
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: A 7 ft 10 in screen 9 ft 7 in from the seat
If it worked: light after dark and privacy exposure no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 7 feet 10 inches and about four inches either way changes whether it works.

+4 hours of usable time on this day. Opens 7:00 PM to 11:00 PM.

Summer solstice, 21 June: 3 hours usable now, 4 hours with this change. 1 hour gained.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanent

An 8 ft 2 in awning

ForecastWorksfrom No

An 8 ft 2 in awning fixes light after dark and privacy exposure.

A folding-arm awning projecting 8 feet 2 inches from the house wall at about 8 feet 6 inches, retracted out of season.

Gained: Light after dark
Privacy exposure
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: An 8 ft 2 in awning
If it worked: light after dark and privacy exposure no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

+4 hours of usable time on this day. Opens 7:00 PM to 11:00 PM.

Summer solstice, 21 June: 3 hours usable now, 4 hours with this change. 1 hour gained.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanentYears to work

An evergreen hedge to about 7 ft 10 in

ForecastWorksfrom No

An evergreen hedge to about 7 ft 10 in fixes light after dark and privacy exposure.

A dense evergreen hedge grown to about 7 feet 10 inches and 9 feet 5 inches along, on the line to Right neighbour's bedroom. It reads as garden rather than barrier, and it will take several seasons to do the job.

Gained: Light after dark
Privacy exposure
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: An evergreen hedge to about 7 ft 10 in
If it worked: light after dark and privacy exposure no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 7 feet 10 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestMove itYou can undo it

A second seat 19 ft 8 in south

ForecastTightfrom No

A second seat 19 ft 8 in south moves this from No to Tight without solving any single limit outright.

Put two chairs 19 feet 8 inches to the south and leave the main table where it is. The point is not to fix this spot but to stop needing it at the hour it does not work.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A second seat 19 ft 8 in south
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Mark 19 feet 8 inches out on the ground and stand there before committing. The geometry is only as good as that distance.

+4 hours of usable time on this day. Opens 7:00 PM to 11:00 PM.

Summer solstice, 21 June: 3 hours usable now, 1 hour with this change. 2 hours given up.

Winter solstice, 21 December: 0 hours usable now, 4 hours with this change. 4 hours gained.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

On this day: light after dark is what keeps it shut, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

On the summer solstice: light after dark is what closes it, and The floodlight is the light doing it. With this change, nothing named closes the usable span.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

TestMove itYou can undo it

Move the table 6 ft 7 in east

ForecastNostill No

Move the table 6 ft 7 in east does not move this in any way worth the effort.

Slide the seating about 6 feet 7 inches toward the east and change nothing else.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Move the table 6 ft 7 in east
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Mark 6 feet 7 inches out on the ground and stand there before committing. The geometry is only as good as that distance.

It does not meaningfully change the beam in either season.

TestMove itYou can undo it

Change The floodlight to a warmer lamp

ForecastNostill No

Change The floodlight to a warmer lamp does not move this in any way worth the effort.

Swap The floodlight for a 2200 kelvin lamp of the same output. Blue-weighted light scatters more in the air, spills further into the garden and reads as harsher at the same brightness. Nothing structural changes; it is a lamp.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Change The floodlight to a warmer lamp
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try it on the plan, then go outside and see.

It does not meaningfully change the beam in either season.

TestAn afternoonYou can undo it

Two low shielded lights instead of one high one

ForecastNostill No

Two low shielded lights instead of one high one eases the hour without solving any single limit outright.

Add a pair of shielded 200 lumen fixtures at knee height near the seating, so the useful light is where people are rather than thrown across the garden.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Two low shielded lights instead of one high one
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 1 foot 8 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestAn afternoonYou can undo it

Shield The floodlight

ForecastNostill No

Shield The floodlight does not move this in any way worth the effort.

Fit a full cut-off shield to The floodlight so the output goes down rather than sideways. The light on the table barely changes; the light on the neighbour's wall mostly stops.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Shield The floodlight
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try it on the plan, then go outside and see.

It does not meaningfully change the beam in either season.

TestAn afternoonYou can undo it

Add 1 ft 6 in of trellis to Board fence

ForecastNostill No

Add 1 ft 6 in of trellis to Board fence does not move this in any way worth the effort.

An open trellis panel on top of Board fence, taking it from 5 feet 11 inches to 7 feet 5 inches. Open trellis blocks a sightline at an angle while letting light and air through, which a solid board does not.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Add 1 ft 6 in of trellis to Board fence
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 7 feet 5 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestA projectYou can undo it

A shade sail over the seating

ForecastNostill No

A shade sail over the seating does not move this in any way worth the effort.

A sail about 16 feet 5 inches by 13 feet 1 inch, set at about 9 feet 2 inches and angled to shed water.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A shade sail over the seating
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 9 feet 2 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestA projectYou can undo itYears to work

A deciduous climber on tensioned wires

ForecastNostill No

A deciduous climber on tensioned wires does not move this in any way worth the effort.

Wires strung about 8 feet 6 inches above the seating with a vigorous deciduous climber trained across them. In leaf it shades like a light pergola; bare, it gives back most of the winter sun a solid roof would have kept.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A deciduous climber on tensioned wires
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 9 feet 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanentYears to work

A deciduous tree 16 ft 5 in west of the seat

ForecastNostill No

A deciduous tree 16 ft 5 in west of the seat does not move this in any way worth the effort.

A medium deciduous tree planted 16 feet 5 inches to the west, grown to about 26 feet, with a crown roughly 19 feet 8 inches across.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A deciduous tree 16 ft 5 in west of the seat
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 26 feet and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanent

Raise the seating 1 ft 6 in

ForecastNostill No

Raise the seating 1 ft 6 in does not move this in any way worth the effort.

A raised platform lifting the seat about 1 foot 6 inches. It clears low boundaries, reaches faster air, and it works both ways: what you can see over, you can be seen over.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Raise the seating 1 ft 6 in
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 1 foot 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanentYears to work

A tree between the seat and Left neighbour's landing window

ForecastNostill No

A tree between the seat and Left neighbour's landing window does not move this in any way worth the effort.

One multi-stemmed tree grown to about 23 feet, set roughly a third of the way toward Left neighbour's landing window. Interrupting a downward sightline needs height, not length, and a single crown in the right place does what a whole run of fence cannot reach.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A tree between the seat and Left neighbour's landing window
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 23 feet and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A pergola with open slats

ForecastNostill No

A pergola with open slats does not move this in any way worth the effort.

A pergola about 13 feet 1 inch square at 8 feet 6 inches with open slats, slats running roughly north.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A pergola with open slats
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

An adjustable louvred roof

ForecastNostill No

An adjustable louvred roof does not move this in any way worth the effort.

A louvred roof about 13 feet 1 inch square at 8 feet 6 inches, blades running north and closable.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: An adjustable louvred roof
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A paler paving

ForecastNostill No

A paler paving does not move this in any way worth the effort.

Replace Concrete pad with a paler paving of similar mass. The surface itself runs cooler underfoot; the trade is that more light bounces back up at a seated person.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A paler paving
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A solid canopy over the seating

ForecastNostill No

A solid canopy over the seating does not move this in any way worth the effort.

A solid roof about 11 feet 2 inches above the seating, 13 feet 1 inch by 11 feet 6 inches, guttered on the low edge. Unlike fabric it works in rain, and unlike a pergola it takes the winter light too.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A solid canopy over the seating
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 11 feet 2 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

Horizontal fins above the opening

ForecastNostill No

Horizontal fins above the opening does not move this in any way worth the effort.

A run of fixed horizontal fins projecting about 2 feet 4 inches from The house, set above head height. Geometry does the work: high summer sun is cut, low winter sun passes under, and the view out is barely touched.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Horizontal fins above the opening
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A ventilated timber deck instead

ForecastNostill No

A ventilated timber deck instead does not move this in any way worth the effort.

Replace Concrete pad with a ventilated timber deck. Heavy paving charges all afternoon and radiates back until well after dark, which is why an evening terrace can feel hotter than the air. A light deck over an air gap is done within the hour.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: A ventilated timber deck instead
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

Take up the paving and plant it

ForecastNostill No

Take up the paving and plant it does not move this in any way worth the effort.

Lift Concrete pad and plant it. Nothing else on this list moves surface temperature as far: paving in full sun sits twenty degrees or more above the air, while planted ground transpires and typically sits at or below it. It is also the only change here that gets better rather than worse over ten years.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Light after dark
Privacy exposure
Still unanswered: Nothing here.

The test: Take up the paving and plant it
If it worked: The hour is easier, even if no single limit disappeared.
If it didn’t: If light after dark still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.