One of the most reported times for homeowners to have outbursts of ghostly activity occurs when they are renovating. Why is that?
Most people assume that renovations in a house must upset the ghosts and get them angry about changes being made.
I think this is a very simple way of looking at it. That is looking at it from the viewpoint of the living, as we think it would be sad and lonely to be dead and we would miss people and places here.
Let's shift that perspective to the spirit world being a parallel realm. We share the same arena, but in different ways. Sometimes, in the right conditions, we sense each other. Perhaps other times, it is not even spirit activity we are dealing with.
Let's look at some possible elements involved -
The Living
There are occupants of the home affected by change. Perhaps adding a window brightens up their disposition or possibly exposure to chemicals and inhalants/molds make them feel poorly. These are environmental factors. 
When we build a home, we are creating an artificial environment devoid of overhead sunlight, wind, live plants, soil, and the living microbial earth, as well as direct exposure to atmospheric and geologic forces.
We may even shield ourselves further with a foundation that keeps moisture and radon out, but also perhaps other earth energies.
We regulate the environment with air-conditioning and heating, fireplaces and even cook in the closed spaces, in rooms that have walls stopping flow of energy.
In fact, we have erected a potential spirit vessel.
Why are so many homes haunted as compared to the outdoors? Perhaps for the simple reason they were built to hold the life energy of the living who resided inside.
The humans within a home may be having either transitional issues with a home that they do not know well (having just moved in) or their perceptions are colored by knowledge of the home's past or its age.
They might be affected by the chemical releases in the environment or the change in pathways of energy. Try and sleep with a mirror facing your bed and then take it away. See what happens to your sleep/dream state.
Changes in the home can alter your ability to relax, cause tension, or create subtle environmental changes that make us paranoid, anxious or even depressed.
Sometimes, it is simply psychological -
Which bathroom would you feel is clean, bright, spacious and soothing? Which feels dark, cluttered, busy, and dungeon-like? Those very visual cues can sometimes alter how we feel in a space. How many people like unfinished basements?
Another consideration is psychokinesis (movement of objects by will/thought). Some people have latent PK abilities that show themselves at certain times of stress. I have had such phenomena around me and it has always come when I am holding in anger and not expressing it or doing anything about it. In small bursts, I have object movement, always with items made with metal, i.e. Christmas ornament hooks, bobby pins, oven door handle, canned foods....
Once we have moved past the living explanations, let's see how many other possibilities are on our list of culprits for renovation disruption.
Released Residual
It is possible that renovation can release residual events from an area of a home that are held like a recording in the environment. These could start playing when that spot is being activated by change or the presence of the living. 
Remember, the people within a building a part of the chemistry of that vessel. An empty building versus a crowded one is a completely different chemistry.
When I was a child, we had a shadow-like ghost that walked the end of the hall into the tiny end bedroom and seemed to disappear in the closet. But, this was not always a closet.
Homeowners in the early 1900s added the closet as a necessary in modern times. It was built over a chimney that was once providing a fireplace for the room. This figure was attending the fireplace that was now covered over by boards and a closet. That is not to say that a spirit was hoping to start a fire, but thata regular event in the past (someone attending the fire) was replayed like a film in that space.
This is a fine example of renovation not affecting the flow of residual or "play back" memories in the home. In fact, many report ghosts walking through walls or seeming to enter from places that have no entrance. This visual we get under the right conditions will play, no matter what how the setting changes. This is one unexplained activity not necessarily activated by renovation; although exposing a once not used area could bring about never before observed residual replays.
This also makes one wonder that if an event can be held in a place to replay in a loop, perhaps nothing ever really ends, just that our perceptions don't see all history in a place at one time. Maybe under the right conditions we see those moments that have never truly left.
Feng Shui "Qi" Energy
There is energy from the earth and spirit realm combined, that traps bad energy, and sadly can also let good energy escape.
The Chinese metaphysical practice of Feng Shui is based on the principle that the natural forces of earth, spirit, the universe and humanity take paths of no resistance and that the way things are laid out within an architecture can determine if positive or negative energies rule or get trapped and linger.
Energy follows pathways. Disruption of the elements in that pathway can cause issues and imbalances; positive and negative events.
For example, a couple bought a duplex in the Detroit. They had plans to break apart the duplex and make it into a single-family home. They moved into one side of it while they began renovations and found that every night they were awakened to footfalls in the hallway. It was a short hall that led to the bathroom and another bedroom. They pondered what other noises the house might make as they lived there longer, but that seemed to be the only issue and it was every single night!
They got to work on renovating the kitchen and bathroom but the wife, anxious to open the house up, insisted the husband finally break through the hallway wall to the other side and allow them more air flow and a better idea of what it would look like.
The wall was torn down, opening the hallway up to more hallway on the other side, creating a long corridor of the original house. Air flowed, the house felt less narrow, and the wife was pleased.
But, that night as they lay in bed talking about renovations, they both quieted down to finally nod off when it occurred to them that there were no footfalls.
The husband got up to inspect, but there were no sounds. They both lay there bracing for the noises that never came. And, they never came again.
Opening up the passageway of the hall also made it possible for both windows at each end of the now conjoined hall to face each other once again and allow free flow of energy in and out without being trapped. At least, that is what Feng Shui concepts would demonstrate.
Areas of a home that can have trouble include dark areas, improper placement of mirrors, clutter, cul-du-sac like areas where energy from windows, stairways, halls that should have a straight through, get blocked.
If you do move into a home, you immediately begin laying out furnishings in areas that perhaps have never been closed off by a sofa or chair. What if you place a mirror across from a window (creates an alley of stimulating energy that keeps you keyed up), or you change the colors of the room (certain colors create different fortune or misfortune), affecting its very energy and balance?
You might move in and change building materials, or decide to go with the open concept floor plan. Maybe you peel away wallpaper for new plaster and paint....
The question becomes - what have you changed in the way the home receives energy, distributes it, allows it to move on, holds negative energy, or attracts positive events?
Even if you don't believe in the concepts of Feng Shui, a respect for ancient studies of energies, leylines, placement, textiles, and orientation as a precise criteria for peace and success, should be considered. But, there are other levels in which disruption can cause chaos.
When you bring home a new item to your home, sometimes it clashes with other existing items. This is something inherent in the imprinted energies on that item. It's like buying an antique and then suddenly having things go wrong. Many think the item is haunted when, in fact, it is holding energy that may not be compatible with the other items.
This is what we might find in a home being renovated, materials, placement, and even the people living there that somehow contribute to a disruption in energies that had been laid down for decades, even centuries. You are creating a new milieu for which the vessel (a sort of dynamic entity) is being affected.
When you open up a wall, remove brick, expose old wood floors, you are releasing all those memories, all that energy, and perhaps the very "tags" that help spirits know where to connect. Everything you have touched and had contact with, you left an essence of you. You are simultaneously everywhere you have been. Imagine placing a chair where a dying bed once was or perhaps tearing down a wall to make energies from two spaces that have remained separate, now colliding?
Quantum Entanglement
So broadly speaking, altering one alters the other (see link at bottom of the post for quantum entanglement link to article).
As a psychometrist, I will say that we do leave a bit of our self information in objects and spaces. Everywhere we have been, we are still there in a sense.
If the spirit realm involves a body-less existence that does not need to be in one location at any given time, then wherever that spirit has wandered in the mortal years here, has left a sort of involvement with that space. What happens to one, happens to another. The spirit senses disruption in a location it has been. Even though its contact was long ago, it can still activate as an essence of their spirit is always present.
With no barrier of time and space to a spirit form, you can disrupt a place that person was in their physical realm, leaving a bit of their spiritual residue, and you get a reaction in our present time that could have been laid out a century ago by the person who touched it.
In other words, a spirit may be reacting in what seems like the present to us but is actually a reaction from the past being released again in this physical realm.
If the spirit realm involves a body-less existence that does not need to be in one location at any given time, then wherever that spirit has wandered in the mortal years here, has left a sort of involvement with that space. What happens to one, happens to another. The spirit senses disruption in a location it has been. Even though its contact was long ago, it can still activate as an essence of their spirit is always present.
With no barrier of time and space to a spirit form, you can disrupt a place that person was in their physical realm, leaving a bit of their spiritual residue, and you get a reaction in our present time that could have been laid out a century ago by the person who touched it.
In other words, a spirit may be reacting in what seems like the present to us but is actually a reaction from the past being released again in this physical realm.
This is a very broad description, but we should start looking past the old-fashioned one body/one soul sense of us becoming invisible humans when we move on and start seeing us as part of a universal collective - everywhere with no sense of past, present or future, simply omnipresent.
Spirit-less Energy
It's possible we might clash with existing energies that are not spirit related. These may be simply part of what makes up the universe and that we may have an affect on, as well it affecting us.
This can include all the energies left on objects and spaces from those who have been there and events from the past, a sort of residue that lingers. This is kind of like the way your joints ache when barometric pressure changes; you are being affected by a force of nature. Or, in the case of cold weather, you breathe out and add warm humidity to the chilly air, producing a frosty breath and affecting the environment.
Another example of this is negative ions. Moving water and even the burning of sage and incense can create negative ions which have a very positive effect on our minds, a sense of peace, confidence, and even euphoria. This is a force of nature that is affecting us. If you lived near a waterfall, you might experience this daily.
But, what forces are held within walls that close in energies creating cul-de-sacs or light waves that affect our eyes and therefore the brain or the pineal gland that is affected by light? Simply having a cheap alarm clock near the head of the bed can put off enough electromagnetic field energy to unsettle the sleep and dream state.
Other factors could be geomagnetic forces, electrical (high tension power lines), bad wiring, radon, geology, photons, you name it! Tons of things in our environment differ depending on structure and how do we (or even the space we live in) react to these changes?
There might be factors in the very milieu of the home including chemical, magnetic, barometric, electric, and more. These could create either unusual perceptions or possibly spontaneous outbursts that affect electrical and movement of objects. Combine this in any manner and you may get some very odd "unnatural" activation. Look what sounds can do -
This can include all the energies left on objects and spaces from those who have been there and events from the past, a sort of residue that lingers. This is kind of like the way your joints ache when barometric pressure changes; you are being affected by a force of nature. Or, in the case of cold weather, you breathe out and add warm humidity to the chilly air, producing a frosty breath and affecting the environment.
Another example of this is negative ions. Moving water and even the burning of sage and incense can create negative ions which have a very positive effect on our minds, a sense of peace, confidence, and even euphoria. This is a force of nature that is affecting us. If you lived near a waterfall, you might experience this daily.
But, what forces are held within walls that close in energies creating cul-de-sacs or light waves that affect our eyes and therefore the brain or the pineal gland that is affected by light? Simply having a cheap alarm clock near the head of the bed can put off enough electromagnetic field energy to unsettle the sleep and dream state.
Other factors could be geomagnetic forces, electrical (high tension power lines), bad wiring, radon, geology, photons, you name it! Tons of things in our environment differ depending on structure and how do we (or even the space we live in) react to these changes?
There might be factors in the very milieu of the home including chemical, magnetic, barometric, electric, and more. These could create either unusual perceptions or possibly spontaneous outbursts that affect electrical and movement of objects. Combine this in any manner and you may get some very odd "unnatural" activation. Look what sounds can do -
Spirit Attachment "Tags"
What if the people who have lived in that building in the past, through their encounters with the space, left a sort of "tag" or "marker" on the spot so that in the spirit realm, if that tag or marker is disrupted, it brings their soul a calling to a place on this plane that they had once inhabited?
For example, let's look at a plane's transponder, it helps us to find the location of the plane. Perhaps humans, through our very spiritual, chemical and electrical systems, leave a "ping" in the environment we have interacted with.
This is a rather universal and psychometric view of how we are right now haunting everywhere we have been with a part of our spirit.
It is not so much that the spirit needs to be one unit as we are in a physical realm. Spirit could be an entirely liquid intelligence that can be all over the universe in a quantum entanglement manner in which what happens to the spirit's essence in one area is felt by the spirit's essence in another area. This would be that new-age-sounding concept of us being part of the universality and connected with All.
As a psychometrist, when I psychically read an object, I am gathering information about the people who have had contact with the object. They obviously deposited somehow their collective knowledge. I see this as a universal "broth" and others might see as Akashic Records, but it is the source throughout the universe that we rejoin in spirited form once we leave the mortal plane. We become full-time associated with the entire universe with no past, present or future.
While living, we are a bit distracted by the physical mortal needs to pay heed to that universal collective, but at times we feel it deeply in a good church sermon or when we come together for a good cause or to comfort those who have had losses. In those moments, we feel the timeless connection to all.
Conclusion
We spend a lot of time considering aesthetics when we are renovating a home, or maybe practicality, but we are also coming into an artificially created environment that has geology, history, and construction and we are disrupting that further.
Sometimes, it pays to consider improving the function and the mood of a space. It takes a bit more time and thought, but things like light and flow and lack of clutter are very helpful to keep a place balanced.
Why is your house acting up when you begin renovation? It can be any number of factors, but in general once the dust settles literally, it does so figuratively, as well.
Eventually, the building accepts the new reality or the spirits within. It is rare that a renovation disrupts permanently, but once again it might be time to recheck the Feng Shui layout of the rooms, windows, mirrors, items, colors, and more.
Where I grew up in the Civil War hospital estate, we drilled a hole in a wall downstairs and one in the floor in the hall above so we could hold up a light and see into a secret room that was covered over by oddly angled fireplaces. We found a stool of some sort, cloth, paper.... You don't generally build a room around debris, so we assume it might have been an underground railroad hiding hole and it would have been ideal with some loose bricks in the fireplace.
When we drilled, however, we had some very extreme disruptions and activity in the home, more than usual, with objects moving, doors slamming, and the like. We put a painting over the hole in the wall and a rug over the hole in the floor upstairs and it settled right back down.
Had we released residual terror of those who had hid in the room? I tend to think that is quite possible, but it was remedied, so we moved on and didn't think about it again.
It's disrupting enough tearing a house apart, but it changes the dynamics and even the spirit (or spirits) of the home.
Will you ever know the exact cause of the issues? Probably not, as these concepts cannot be proven yet.
You might consider keeping a journal when you go to renovate and make note of anything that you've had issues with before the renovation and then any issues after including the location in relation to the renovation area, quality, intensity, when it got worse (Did you just finally knock out a wall or change electrical?). This includes regularly photographing items when you settle down for the night and then again in the morning. You might be surprised how many renovation tools and items move!
I always encourage journal writing as a way of finding patterns and repeat-ability. In fact, if an issue arises, like object movement after you tear down a wall, try draping something up where the wall once was and see if the issue stops for a time. Experiment. This is your living lab.
Just know that eventually the house and any occupants settle down into the new reality.
Sometimes, it pays to consider improving the function and the mood of a space. It takes a bit more time and thought, but things like light and flow and lack of clutter are very helpful to keep a place balanced.
Why is your house acting up when you begin renovation? It can be any number of factors, but in general once the dust settles literally, it does so figuratively, as well.
Eventually, the building accepts the new reality or the spirits within. It is rare that a renovation disrupts permanently, but once again it might be time to recheck the Feng Shui layout of the rooms, windows, mirrors, items, colors, and more.
Where I grew up in the Civil War hospital estate, we drilled a hole in a wall downstairs and one in the floor in the hall above so we could hold up a light and see into a secret room that was covered over by oddly angled fireplaces. We found a stool of some sort, cloth, paper.... You don't generally build a room around debris, so we assume it might have been an underground railroad hiding hole and it would have been ideal with some loose bricks in the fireplace.
When we drilled, however, we had some very extreme disruptions and activity in the home, more than usual, with objects moving, doors slamming, and the like. We put a painting over the hole in the wall and a rug over the hole in the floor upstairs and it settled right back down.
Had we released residual terror of those who had hid in the room? I tend to think that is quite possible, but it was remedied, so we moved on and didn't think about it again.
It's disrupting enough tearing a house apart, but it changes the dynamics and even the spirit (or spirits) of the home.
Will you ever know the exact cause of the issues? Probably not, as these concepts cannot be proven yet.
You might consider keeping a journal when you go to renovate and make note of anything that you've had issues with before the renovation and then any issues after including the location in relation to the renovation area, quality, intensity, when it got worse (Did you just finally knock out a wall or change electrical?). This includes regularly photographing items when you settle down for the night and then again in the morning. You might be surprised how many renovation tools and items move!
I always encourage journal writing as a way of finding patterns and repeat-ability. In fact, if an issue arises, like object movement after you tear down a wall, try draping something up where the wall once was and see if the issue stops for a time. Experiment. This is your living lab.
Just know that eventually the house and any occupants settle down into the new reality.
Further Reading
Confessions of a Feng Shui Ghostbuster
Quantum Entanglement Revealing Spooky Shapes
Negative Ions and mood
Earth's geology and makeup
